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Aquarium Lighting

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We are looking for at least 100 PAR intensity on the sand bed and the required color spectrum for your animals.  Stagger corals by placing them on your live rock aquascape at depths (low/sand bed, mid tank, and high) according to their needs.

An article by Carl Strohmeyer (he asks for a link back, but we can't find one for him at this time)

By Carl Strohmeyer
Updated 8/6/10


When choosing your aquarium lighting (especially Reef or Planted Freshwater), there is much more to consider than watts per gallon. In fact the 2-6 watts per gallon for a reef or freshwater plant aquarium, less for fish, more for many corals; is a VERY basic start but that is very general and quite out-dated due to the variety available modern lights with varying lumens per watt lights, different wavelength, focused lumens, PAR output, etc.. Sadly the watts per gallon “rule” for aquarium lighting is still thrown around today despite all the technological advances in lighting which often makes this grossly inaccurate (please read the full article here to understand why the Watts per gallon is only part of the equation for your aquarium light determination).
As you will read more later in this article a watt is simply a measurement of energy NOT light output or even quality. Even comparable lumen output at the lamp is no longer a good measure of lighting parameter performance due to focus and restrike; a good example is a modern LED (such as the
Aqua Ray) which has a vastly higher lumen output than a comparable wattage CFL (such as a Current USA Compact Fluorescent) at 20 inches.

There are other factors effecting lighting for your aquarium than just watt output. For example: You cannot compare the output of a 150 watt Metal Halide to a 150 watt outdoor floodlight. Nor an 85 watt standard incandescent to a
85 Watt 6400 K SHO Bulb. What I am trying to say is sometimes it comes down to comparing apples to oranges.

Other aquarium lighting considerations besides energy used (watts) are PAR (and other wavelength needs of the aquatic environment), Lumens per watt and the amount of space a bulb will occupy which allows for more or less lights depend on the size of the bulb. For example a SHO that uses 105 watts yet is only 10” and placed into a reflector will be very efficient as per wattage and space utilized for this. Another example is a
T-2 bulb that only takes up a small space (7 mm diameter) can be a very productive bulb as per lumens per watt (73 lumens per watt!), PAR and space used. For example I would recommend a pair of 19 inch/13 watt/ 6400K T-2 over a pair of 18 watt standard (T8 or T12) for a 20 gallon planted tank; the reasons are higher lumens per watt (73 vs. 40-50) and correct temperature/PAR (6400 K vs. 2100 -4500).

Another note with freshwater plant light requirements is that the 3-4 watts per gallon general rule applies to medium to high light plant requirements, not low light such as Java Moss, or in the case of Reef Aquariums stony corals such as Acropora.

This overview is just an brief explanation, please read further for more in depth discussion (and I do not assume this article is the end all of aquarium lighting discussion, I will add a lot more as time goes on as newer information that explains or corrects the subjects contained in this article better).  Please see the summary section of this article for more about my “how” and “why” of article writing:
“Aquarium Information”

The four most important criteria in determining the light you need are:
• Lumens per watt
• Lumen focus (as well a restrike, although less of an issue as per my research and tests than focus)
• PAR (this is important to understand as well as related useful light energy)
• Watts (or watts per gallon, however this term is way over used/simplistic)

However the above four aquarium lighting criteria is an over simplification, so an understanding as best possible of other aspects as well as the positives and negatives of each lighting type, including types that the often 5-10 years behind technology aquarium industry ignore such as LED, SHO, T2, or Induction are important as well (as I see it from tests and research the SHO, T2 and especially the LED are future of aquarium lighting, not the popular dual CFL by Current USA & others).

Here are other important factors;

[1] KELVIN RATING (such as 10,000K daylight bulb):

Although the classic interpretation of what Kelvin is in not what is meant by light Kelvin ratings, I believe it should be considered.
Here is a brief description of Kelvin:
Kelvin is defined by two points: absolute zero, and the triple point of pure water. Absolute zero is defined as being precisely 0 K and –273.15 °C. Absolute zero is where all kinetic energy (motion) in the particles comprising matter ceases, and they are at complete rest. At absolute zero there is NO heat energy. The triple point of water is defined as being precisely 273.16 K and 0.01 °C. Here are a few Kelvin numbers:
*Absolute zero = 0K (-273.15C)
*Waters freezing point = 273.15 K (0 C)
*Waters boiling point = 373.1339K (100C)
What the true definition of Kelvin is that is a unit of measure of temperature on the thermodynamic (absolute) temperature scale.

Light Kelvins
Kelvin is used in the lighting industry to define the Color temperature of a bulb. Higher color temperature lamps above 5500 K are "cool" (green–blue) colors, and lower color temperature lamps below 3000 K are "warm" (yellow–red) colors.

Kelvins as applied to color temperature of lights/lamps are derived from the actual temperature of a black body radiator, which is the concept of color temperature based on the relationship between the temperature and radiation emitted by a theoretical standardized material and termed a “black body radiator”. This is where the “classic” definition of Kelvin and that used for lights come together, as hypothetically, at cessation of all molecular motion (the black body state of this hypothetical radiator), the temperature is described as being at absolute zero or 0 Kelvin, which is equal to -273 degrees Celsius.

An incandescent filament is very dark, and approaches being a black body radiator, so the actual temperature of an incandescent filament is somewhat close to its color temperature in Kelvins.

Incandescent lamps tend to have a color temperature around 3200 K, but this is true only if they are operating with full voltage. When a lamp is dimmed below its full potential, its filament is not as hot, and it produces less light. The reduced temperature of the filament also reduces the color temperature downward. An incandescent light dimmed to 10% is considerably more red in color than one at 100%.

Another consideration as to the color temperature as applied to lights; color temperature does not take into consideration the spectral distribution of a visible light source. In cases where a light source, such as a fluorescent lamp, arc-discharge burner, laser, or gas lamp, does not have a spectral distribution similar to that of a black body radiator.

A few notes about Kelvin:
* Plant chlorophyll absorbs light at wavelengths of 300 to 700 nm (a Kelvin rating of about 6400 strikes a good balance here, which is why this is the best Kelvin temperature for freshwater plants and symbiotic zooxanthellae in corals).
* The lower the “K”, the more yellow, then red the light appears, such as a 4500 K bulb.
* The higher the “K”, the bluer the light appears, such as a 20, 000 K bulb.
*Higher Kelvin Color Temperature lights penetrate water more deeply, even more so in saltwater, however there is less of the infrared “PAR spike” as well. * The human eye sees mostly sees light around 5500K.
* Candle flame = 1850 – 1900 K
* Sunlight (1 hour after dawn) = 3500 K
* Typical summer light (sun + sky) = 6500 K
* Cool white fluorescent = 3400 K

What Kelvin rating for Plants & Corals;
Here are some observations made by me and others in the professional aquarium maintenance community, some of these are simple observations, while others were based on more controlled tests.

*The 6500 Kevin bulbs have produced the best freshwater plant growth, and can also work with SPS, LPS placed high in the tank water column (nearest the lights) based on the symbiotic zooxanthellae needs found in these corals. For more depth penetration (& to aid in the first spike in PAR, please see PAR section), blue actinic, 50,000 K/Actinic or adjustable/multiple LED can be added (such as
AquaBeam Marine Blue) can balance out 6500K lamp if used in marine reef tanks.
Please note that saltwater absorbs slightly more light energy than freshwater due to the higher density of the water, so 6500 will not penetrate as deeply.

*The 10,000 Kelvin bulbs also achieve good growth rates, although slower than the 6500 K bulbs in shallow aquariums. 10000 K bulbs have produced excellent growth with soft corals and LPS, although slower paced SPS growth.
The 10,000K can be a good choice for achieving PAR for better depth penetration than a 6500K bulb (such as 20 inch or deeper aquarium)

*The 14,000K light/bulb (often popular with Metal Halide and LEDs), will penetrate even more than the 10,000K light while still providing useful PAR (this would be the highest “Daylight” Kelvin temperature I would recommend and still expect good growth in corals, see PAR section).

*The 20,000 K bulb is more blue yet and brings out all of the fluorescent pigments in many corals (making for a very nice appearance). However the best tests and observations show that when used alone the growth rate of SPS corals come to a complete standstill with 20,000 K lamps. Although maybe a good supplement for appearance, these bulbs are over rated for use as the only reef Kelvin temperature and should be avoided when used as the only Kelvin temperature lights

*The 50,000K is generally the Kelvin rating of an actinic blue light source which is beneficial for the first “spike” in PAR. This temperature light (as with 20,000K) is best used with other light Kelvin Temperatures and is a better choice than the 20,000K light for such combinations. The 50,000K is a good compliment to the 6500, 10,000, 14,000 Kelvin lights, especially for zooanthellic algae necessary for stony corals, clams, and other sessile species.

Kelvin summary
The Kelvin rating is another area of comparing apples to apples in lights, not just watts. Although the above is a simplified explanation of Kelvin as it applies to lights; as such you cannot compare a 6400 K T8 light to a 6400 MH light (the MH is going to have much more output as you will read later).
However (using a CFL as an example, this can apply to any light type), a 6400 CFL will have a higher energy output than a 3500 CFL, this is why an incandescent filament is very low in Kelvin (dark) as derived from the actual temperature as it is just above a black body radiator. Another example using an incandescent light, this time looking at it from the aspect of watts; a 100 watt incandescent has a Kelvin of 2870 while a 40 watt incandescent has a Kelvin of 2500. So as you can see, there is some correlation between energy output and Kelvin Color.
This does not mean that a certain Kelvin bulb is necessarily “better” as factors such as “lumens per watt”, watts, focused lumens and more MUST be considered as well.

Color Temperature in a Virtual Radiator- This is an interesting resource with a virtual radiator worth checking out.

A nanometer scale is used to measure the wave length of light energy from cosmic rays to radio waves. An actinic bulb will have a Nanometer spike at about 420N, a UVC bulb about 265N, and a daylight bulb about 700N. The difference in the wavelength determines how the wave affects its surroundings. It is this wavelength difference that allows short-wave x-ray to pass through walls, while longer-wave visible light cannot pass though the same material; short-wave ultraviolet and x-ray can destroy DNA in living microorganisms and breakdown organic material while visible light will not. All light energy is measured on a "nanometer" (nm) scale. Nanometer means one-billionth of a meter.
This applies to aquariums when we consider the light spectrum and how it applies to our aquariums individual needs: Red light is the first to be filtered out and can only penetrate a short distance. As light waves penetrate deeper into the water, orange and yellow are lost next. Of all the colors of the spectrum blue light penetrates the deepest. Corals need intense equatorial UVA (actinic) and even some UVB as recent articles (and my own experience) suggest. Most plants need a balanced PAR light range (see section about PAR).
The Nanometer scale and Kelvin temperatures come together when applied to aquarium lighting this way; Natural sunlight on a clear day registers at 5500 Kelvin degrees. Kelvin temperatures less than 5500K become more red and yellow and the higher the Kelvin temperature the more blue the light is.
Most photosynthetic invertebrates should be kept with lamps in a varied Kelvin temperature that includes 6400-10,000 K (up to 20,000K in tanks deeper than 30 inches, although I recommend a maximum of 14,000 and then balance with actinic) as well as Actinic which emits a fluorescent blue light and is usually used as supplemental lighting. Not only is actinic lighting somewhat beneficial to photosynthetic invertebrates, it is also aesthetically pleasing to the eye when used to supplement "daylight" lighting.
Freshwater aquarium plants benefit from lighting with a Kelvin temperature in the range of approximately 6500 degrees. Freshwater plants prefer light with more red in the spectrum.

It is also noteworthy than Fluorescent and even more so incandescent lights produce a lot of yellow and green nanometer light, which research indicates is mostly wasted energy in terms of the needs or freshwater plants and SPS Corals. This is where an
LED Aquarium Light, Metal Halide, or even (to a lesser degree) T2 Lights excels as there is much less wasted yellow/green light.

[3] LUX:
A measure of the intensity of light (referred to the photometry of light), one lux is equal to one lumen per square meter. This is important for aquarium plants. Once again this is another area of comparing apples to apples in lights, not just watts.
This is also VERY important to most corals in marine reef aquariums. When the Lux (intensity) is not enough the zooxanthellae (algae that are inside of corals tissues) do not create plentiful oxygen. The minimum light intensity should be no less than 3,000-lux when it reaches the deepest part of the aquarium. You can over light your coral to a light saturation point (quite hard in my experience, but this should be noted), maximum Lux should be no more than 100,000 to 120,000.
By comparison Lux in tropical reefs has been measured to be between 110,000 and 120,000 Lux at the surface of the reef and 20,000-25,000 Lux one meter below the surface.

[4] PAR:

PAR is probably one of the most important considerations along with the related Useful Light Energy, Lumens per Watt, Focused Lumens and Watts per Gallon when choosing a light for your aquarium, yet is often over looked by both marine and freshwater pant keeping aquarists.

PAR is the abbreviation for Photosynthetically Active Radiation which is the spectral range of solar light from 400 to 700 nanometers that is needed by plants for photosynthesis. This is found from actinic UVA to infrared; 400-550nm (of which 465-485 has the highest PAR of the actinic range) which is the absorption bandwidth of chlorophylls a, c², and peridinin (the light-harvesting carotenoid, a pigment related to chlorophyll) and ~620-700nm which is the red absorption bandwidth of chlorophylls a and c².
Photons at shorter wavelengths (Ultraviolet –C or UVC) tend to be so energetic that they can be damaging to cells and tissues; fortunately they are mostly filtered out by the ozone layer in the stratosphere. Green light occupies the middle spectrum (550-620nm; what is mostly visible to us) and is partly why chlorophyll is green due to the reflective properties.
Bulbs that emit mostly actinic light will have a lower PAR (although actinic UVA still occupies an spike in PAR as seen from the graph and improve the PAR of your lighting), bulbs that occupy mostly the middle spectrum (yellow-green) such as “warm White (2700K) will produce little necessary PAR, while bulbs that produce mostly infrared will produce more important PAR (as seen from the graph), however it is the balance of infrared and UVA that will generally provide your best PAR output.

PUR (Photosynthetically Usable Radiation) should also be considered. PUR is that fraction of PAR that is absorbed by zooxanthellae photopigments thereby stimulating photosynthesis. As noted above, PUR are those wavelengths falling between 400-550nm and 620-700nm.

PAR, photosynthetic active radiation graphImportant Definitions as it applies PAR in plants and zooanthellic algae: See the graph to the left as it corresponds to each of these definitions.

*A: Phototropic response; having a tendency to move in response to light. Basically this is the Chlorophyll containing plant or algae "moving" to respond to a positive light source to begin the process of photosynthesis (initial growth of plants, zooxanthellae, etc.).

*B: Photosynthetic response; the process which begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls.

*C: Chlorophyll synthesis is the chemical reactions and pathways by the plant hormone cytokinin soon after exposure to the correct Nanometers wave length (about 670 NM) of light resulting in the formation of chlorophyll, resulting in continued growth of a plant, algae, zooxanthellae and the ability to “feed” and propagate, and without this aspect PAR (670 NM light energy), zooxanthellae and plants cannot properly “feed” propagate. The results of the lack of this high PAR “spike” would be stunted freshwater plant growth, and eventually poor coral health in reef tanks

Further PAR Information; As the reader here can see, there are three main spikes in the PAR spectrum, with all three being important, however the most important spike occur at the red side and all three are generally incorporated more or less in a daylight bulb of approximately 6500K, not just a bulb of only infrared or as is mistakenly believed by many reef keepers, only in the UVA/actinic spectrum (although a daylight bulb of 10,000-14,000K can provide this too for deeper “more dense” tanks as these higher Kelvin bulbs generally penetrate deeper than a 6500K, albeit with slightly less from the 670 NM spike).
This can vary with bulb type though as not all 6500K daylight bulbs are the same, see the Useful Light Energy section.
Unfortunately, despite anecdotal claims passed around within the aquarium hobby; in better funded tests outside the aquarium industry show that many stony corals, clams, and other sessile species that depend on photosynthesis of zooanthellic algae not only thrive but also propagate with light that achieves the optimum PAR, which includes daylight from 6500k to 14000k (Higher Kelvin outputs are required for tanks deeper than 24-30 inches to achieve maximum PAR such as a 14,000K, although high intensity
6400 SHO lamps can generally penetrate deep freshwater tanks well and perform well in marine reef tanks when balanced with actinic/50,000K lights).

*It is also noteworthy that most green algae need more of the actinic spike than “higher plants”, hence the popularity of actinic lights for reef aquariums, however the optimum nanometer range is about 465-485nm, not the lower 420nm many actinic lights produce or the more broad range many “blue” aquarium lights produce of 400-520 nm (this is where the latest technology LED lights “shine”, having a more precise 465-485nm blue). For this reason it is a good idea to have extra actinic for corals/clams that depend upon zooanthellic algae, while at the same time limiting blue/actinic in freshwater aquariums to avoid excessive green algae growth.

More recent studies show that excessive low UVA (under 420nm) and especially UVB radiation can actually bleach coral and in an aquarium environment lights with more UVA or UVB are not generally necessary as although a lamp with more “blue” such as a 20,000 K MH may penetrate more deeply (due to the fact that infrared light gets absorbed the deeper the light must penetrate), this should not be the sole Kelvin color light for most aquariums (better would be to compliment a 6400 through 14000K bulb with a 50,000K actinic bulb)

With this in mind it should be noted that lamps with both red and blue spectrums will do well for plant growth in BOTH freshwater and saltwater, despite some claims that blue is only for saltwater aquariums (there is not a difference in chlorophyll production in freshwater from saltwater that I know of).

Measuring PAR
Although Kelvins (as well as LUX conversions using questionable LUX to PAR conversion factors) are ways of getting rough estimates of PAR, only a Specific PAR Meter (also called Quantum Light Meters) can give you’re the best measurement of this very important aspect of determining your tanks lighting requirements (both at the surface and under the surface)
(Here is a link to a PAR Meter
Apogee MQ-200 PAR Meter)
Currently accepted numbers measured as µMol•m²•sec (also referred to as micro mols or mmol) are 50 mmol for most plants or low light corals such as Nemezophyllia, while Acropra can require PAR outputs as high as 300 mmol (any higher is simply a waste of energy/light)

Further PAR Info
Some organisms, such as
Cyanobacteria, purple bacteria and Heliobacteria, can utilize light in regions such as the low infrared. These bacteria make use of the unusable light discarded by the plant kingdom, in this case, light outside the PAR range required by plants, which is why Cyanobacteria thrive in lighting conditions that include the more yellow 4000 K and below and why actinic (50,000K) as well as balanced light in the 6400 to 14,000K range combined with passing water through an ultra violet sterilizer (to kill free floating Cyanobacteria) is important for control.
In the case of
Red Slime Cyanobacteria, these Cyanobacteria do not use the PAR spikes at 435nm and 675nm and instead utilize more of the middle yellow and green light spectrum that is most common fluorescent (even so-called aquarium fluorescent lights) and incandescent lighting.

Please do not confuse the term PAR (Photosynthetically Active Radiation) used in plant growth as discussed here with another use of the same term in lighting which is Parabolic Aluminized Reflector. This type of light is used for stage lighting and should not be purchased for marine, freshwater, or Greenhouse use under the mistaken belief that these lights are “great” for plant/coral growth.

For further reading (references) about PAR:
*Light and Plants
*A rational approach to light measurements in plant ecology
*Photosynthetically Active Radiation

Fish Health:
Many recent studies have shown the importance of full spectrum lighting (which will generally encompass a high PAR value) as it relates to health in humans, animals and can be extrapolated to fish as well for a disease prevention which is why good lighting should not be restricted to Reef Marine or Planted Freshwater Aquariums, but to fish only salt or freshwater tanks as well.
In fact the medical community is now utilizing 6400K SHO bulbs (& similar full spectrum lights) due to increasing studies that show better immune function, mental health, and more. Animal studies support similar results as well. This need not be a SHO light, but any high PAR/full spectrum light (generally 6500K) T2, T5, LED, CFL, etc.

See these references:
*New Science Sheds Light on Immune Deficiencies
*Light as a Nutrient

[4] Useful Light Energy:

Useful Light Energy, Daylight CFL and LEDThis is a simplistic way to explain light energy that a light/lamp produces that is of little or no use to aquarium life; in particular freshwater plants or marine corals that have high light requirements.
The best way I can explain this is to think about how mixing all paint colors will produce black, while the mixing of all light energy produces white. We as humans may notice this to some degree, however we do not have the ability to pick out particular colors such as a honey bee can.
More to the point, even the best of fluorescent lights that are a Kelvin temperature of 6500 K use a percentage of their light energy in the yellow and green light spectrum which is mostly useless for aquarium plants or corals (LEDs & modern T2s/ T5s do not suffer as much from this problem from what I have observed using this lens).
This is where although a 6000-8000K light generally will provide good PAR often there is also more yellow/green light as well when used in water applications. This is one aspect of higher Kelvin (10,000- 14000K) day light lamp that is more efficient (although Kelvin temperatures much over 14000K loose much of the important 700nm “spike” & should be avoided as the only light source)

The picture above
(Please click on the picture to enlarge) demonstrates this with two 15 Watt CFL (30 watts total) vs. one 12 Watt Marine White LED (all white 14,000K emitters). This picture is taken with a camera that filters out certain wave lengths allowing for a better viewing of the difference which is otherwise not easy to discern, however the picture shows how the LED on the left has less of this wasted yellow and green than the CFL lights on the right.
Otherwise the light output appears the same, although this is still important when you consider that this is achieved with only 12 watts of LED vs. 30 watts of Compact Fluorescent lights.

With some LED Lights, new technology LED emitters can be selected for the exact wavelength of light, thus almost no useless yellow or green light is emitted, so although the LED may seem less bright than some HO lights with the naked eye (such as T5s or MH) the actual output of light energy in spectrums we cannot see is much higher. This is why gauging a light by what you see is highly inaccurate.

PAR, human visible light, green, yellow graphThe graph to the left shows 'A' the main PAR curve while 'B' is what we see with our own eyes. The reason for displaying this is that many lights commonly marketed appeal to CRI, which does not mean optimum PAR, as well most fluorescent aquarium/plant/reef bulbs still have much of their energy in this basically more useless band of light energy in the middle. This includes most fluorescent bulbs, although the newer T2 and some T5s have less waster energy in this yellow/green band width than others.


The international unit of luminous flux or quantity of light used as a measure of the total amount of visible light emitted. The higher the lumens, the “brighter” or more “intense” the light looks to the human eye. You can figure lumens per watt by dividing the lumens your lamp lists by the wattage the fixture lists.

Knowing your lumens per watt is often as or more important than watts per gallon. For example a T12 light that is rated at 20 watts with a total lumen output of 800 lumens has a lumen per watt output of 40. While a
13 watt T2 bulb rated at 950 lumens has a lumen output of 73 lumens per watt. This is a clear example that the watts per gallon rule is severely flawed as the 13 watt T2 (or two of these) is clearly the better choice for a 15 gallon planted aquarium (or reef) and this does not even take into consideration the PAR rating which is also important for plants/corals or lumens per length of bulb (space). This lumen comparison also applies to SHO, VHO, and Metal Halide all of which far out produce most T12 lamps in lumens per watt.

Focused Lumens
It is also noteworthy that even the lumen output can be deceiving when considering aquarium lights;
LED are a good example of this as these newer technology lights have extremely focused light energy with little essential light energy lost (such as by Restrike), unlike almost every other type of aquarium light currently available. With this focused energy a LED often requires half the lumens (or often even less) to provide essential light energy (such as PAR) to plants, corals, etc. The newer generation LED lights have considerable less loss of lumens at 20 inches than a CFL light (as per tests that show 166% more lumens for the same wattage LED as compared to a common CFL of equal wattage). As another example, think lasers, although not nearly as focused as a laser, modern LED emitters (such as the Aqua Ray) are much more focused than other types of commonly used aquarium lights.

[6] WATT:
Watts equal one joule of energy per second. For us, it’s a measurement of how much energy our light fixture is using NOT of light output! This why the 2-3 watts per gallon for FW plants (3-5) for reef can be deceiving, and this rule is only a starting point similar to the 1 inch of fish per gallon “rule”. This archaic rule was more accurate when all that was used were T12 lamps which is what this rules is based on.
Keeping this in mind the average T12 has a lumens per watt rating of 40, which means you would need half as many watts of a bulb that produces 80 lumens per watt (assuming PAR, Kelvin and other aspects are equal)

The term “watts per gallon” is getting more archaic as newer T-2, T-5, compact Fluorescents, the SHO, and especially the new reef compatible LED lights have more watts spread over less distance. Keeping this in mind; ‘watts’, when applied to a standard fluorescent tube are spread over longer bulbs as the wattage increases. For instance a standard 30 watt T 8 bulb is 36” while a standard 20 watt T-8 bulb is 24”. For high light requirements such as plants or reefs, at least 1 inch per watt is required when comparing tube style fluorescents bulbs.
Many high output light such as the Metal Halide or the more economical
SHO PC bulbs use a lot of watts in a small amount of space. The 110 watt SHO bulb uses 110 watts in 10” or even less if mounted in a pendant.

Another aspect of watts is the output of lumens per watts actually used. The output of a 400 watt incandescent bulb is about 25 watts of light, a 400 watt metal halide bulb emits about 140 watts of light. If PAR is considered to correspond more or less to the visible region, then a 400 watt metal halide lamp provides about 140 watts of PAR. A 400 watt HPS lamps has less PAR, typically 120 to 128 watts, but because the light is yellow it is rated at higher lumens (for the human eye).

[7] CRI:
To help indicate how colors will appear under different light sources, a system was devised some years ago that mathematically compares how a light source shifts the location of eight specified pastel colors on a version of the C.I.E. color space as compared to the same colors lighted by a reference source of the same Color Temperature. If there is no change in appearance, the source in question is given a CRI of 100 by definition. From 2000K to 5000K, the reference source is the Black Body Radiator and above 5000K, it is an agreed upon form of daylight.

A CRI of 100 has a heavy red spectrum. The color temperature is 2700 K for incandescent light and 3000 K for halogen light. An incandescent lamp, virtually by definition, has a Color Rendering Index (CRI) close to 100. This does not mean that an incandescent lamp is a perfect color rendering light source. It is not. It is very weak in blue, as anyone who has tried to sort out navy blues, royal blues and black under low levels of incandescent lighting. On the other hand, outdoor north sky daylight at 7500K is weak in red, so it isn't a "perfect" color rendering source either. Yet, it also has a CRI of 100 by definition.

CRI is useful in specifying color if it is used within its limitations. Originally, CRI was developed to compare continuous spectrum sources whose CRI's were above 90 because below 90 it is possible to have two sources with the same CRI, but which render color very differently. At the same time, the colors lighted by sources whose CRI's differ by 5 points or more may look the same. Colors viewed under sources with line spectra such as mercury, GE Multi-Vapor® metal halide or Lucalox® high pressure sodium lamps, may actually look better than their CRI would indicate. However, some exotic fluorescent lamp colors may have very high CRI's, while substantially distorting some particular object color.
Technically, CRI's can only be compared for sources that have the same Color Temperatures. However, as a general rule "The Higher The Better"; light sources with high (80-100) CRI's tend to make people and things look better than light sources with lower CRI's.
Why use CRI if it has so many drawbacks? It's the only internationally agreed upon color rendering system provides some guidance. It will be used until the scientific community can develop a better system to describe what we really see. It is an indicator of the relative color rendering ability of a source and should only be used as such (Source:
Color Rendering)

To be blunt, CRI is not a parameter that is important in determining the best aquarium light, but it is included here since many mistakenly tend to consider it an important parameter


Aquarium Light Types Explained Here Include:
• T8 & T12, • T5, • T2
• VHO, • CFL, • SHO
• Metal Halide, • LED
• Induction, • HID Xenon

*T-12; a standard pin, 1-1/2” wide bulb. This bulb will generally use more watts and have a lower lumens per watt ratio (usually around 40) and is common in shop lights and even many aquarium bulbs. These are generally the least expensive lamps to purchase and even though they may be “old school”, these still may make up for there low technology with the fact you can purchase several for a low price to make up for poor efficiency. The main caution I would add to these of these bulbs for aquariums is many forums often suggest the use of shop lights as an inexpensive alternative to many aquarium lights, however a 4100 K cool white shop light is not going to come close to a 6400 K daylight lamp that is of peak PAR efficiency (even if you match lumens).

*T-8; a standard pin, 1” wide bulb. As compared to the T-12, a 48” T-12 will use 32 watts, while a 48” T-8 will often use 32 watts (although not always). This is the more common bulb/lamp size in many basic aquarium lights.

*T-5; Generally around 13 mm in diameter. This is a mini pin bulb which generally uses even less watts per lumen than many than T-8 bulbs. A common lumens per watt output for T-5 lamps is around 65. The T5 has become very popular among both plant keeping freshwater aquarists and reef keepers for good reasons; they are compact, come in many varieties and high lumen per watt outputs.

• One negative with T5s is that the quality control on these lighting fixtures (not the bulbs themselves) is often lacking. The problem has been with some fixtures and ballasts.
This problem tends more with the HO (or VHO) T5 light ballasts/fixtures, and in fact tends to be a problem with VHO Compact Light Fixtures as well. For this reason my recommendation is to avoid the VHO or HO T5 or Power Compact CFLs and stick with the standard output versions. If higher output is needed consider the newer technology SHO, LED or MH lights instead, in fact when cost per lumen as per lifespan is considered, a
LED Aquarium Light Fixture is now a much better deal (since LEDs last 50,000 hours vs. the common 8000 lifespan of a HO T5 or VHO Power Compact).

Another consideration for higher output requirements, such as large planted freshwater aquariums, consider the vastly superior in terms of performance and cost SHO light over the T5 (the T5 is a good light, but it is often pushed by aquarium keepers that are not aware that technology has passed them by).

T2 Aquarium Fixtures, Lights*T-2; These bulbs are the latest fluorescent technology yet (LED are advancing even more).
They measure only 7 mm and allow for several bulbs in a small space. A 13 watt 20 inch T-2 Bulb (6400 K) produces 950 lumens which is 73 lumens per watt in a very small space with low wasted green/yellow light energy that is often found in other Power Compact Lights!
Quite bluntly, these
T2 lamps and fixtures are about the best bulbs in a small space I have seen! These are very useful for small to medium planted aquariums or Nano Reefs or even shelves for betta breeders. The linkable fixture feature (although some T5s also have this neat feature) is also a nice aspect of these T2 lights/fixtures (this allows for use in larger aquaria such as 60 gallons PLUS). Some T2s can be linked with small extensions (that are available with these T2 fixtures), these allow you the choice of either placing a T2 in series (end to end) or in parallel (which is useful if you desire a higher output yet in a small space or to utilize a daylight and blue/actinic light parallel to each other) with out having to add multiple outlets/plugs.

The newest generation T2 Lights require less watts to provide the same useful light energy (in particular required by plants & coral) than all other lights except for LED.
Speaking of LED Lights, the T2 makes an excellent compliment to LED Lights (for cost savings as well). The picture to the left displays a newly set up planted freshwater tank that has 4
GroBeam 500 LED and 4 6400K T2s as well as a Mylar Reflector (there are many locations selling Mylar including online)
(Please Click the picture to enlarge)

When all important parameters are considered (PAR, useful energy, lumens per watt, etc.) the a typical 6400K T2 about 40% of the wattage of a standard T8/T12 aquarium light for the same useful output (a 13 watt T2 will equal 30 watts of most older fluorescent aquarium lights). The T2 will even exceed a comparable T5 light by about 20%.

I expect these new T-2 lamps to sweep the small to medium aquarium keeping hobby (especially planted FW and Nano reef) due to their extremely high efficiency and out put. (only LED lights are more efficient, please click on the picture to the left for a comparison).
In fact these lamps are even a good choice for many aquariums such as 60 gallons and larger since each fixture can be linked together forming a larger fixture (similar to some T5 fixtures, which are also good fixtures, just not quite up to the more modern T2 in efficiency vs. output). For instance I have used two T2s linked together for some 60 gallon FW aquarium and two sets of two (placed in parallel in the hood) for planted 60 gallon FW aquariums.
T2 Fixtures/lights also work well in Marine Aquariums (particularly pico/nano reef) since these lamps in the 6400 K version have a high output in PAR required for symbiotic algae that live within corals. As well
actinic/blue versions of the T2 light are now available to the consumer.

One negative with the first generation T2 as compared to the older T5 is that there are not the selection/variety, however as noted in the previous paragraph, blue/actinic T2 lights are now available to the hobby.
As well, there is not as much need for some of the versatility other lights, as the T2 has its own versatility such as small space combined with higher lumen per watt output. I would also counter uninformed aquatic forum comments such as this one:
“T2 are still pretty much a niche market that could be easily overwhelmed by the T5 and they could disappear at any time or just become even more expensive”. The answer is both yes and no. The T5 at one time was still a niche market as well, and more importantly the T2 has grown considerably popularity in Asia (possible due to space concerns) and even in small scale Hydroponics/home green house applications in North America. Statements like that are why the aquarium industry is often a decade behind other industries in adapting new technologies (if at all in some sad occasions).

One other negative with first generation T2s that goes for T5s (especially the expensive HO version of T5) is that the quality control on these lighting fixtures (not the bulbs themselves) is often lacking. From my investigation of looking at defective items, it seems to be difficulties in good solder in the confined spaces of these small micro lighting fixtures. This problem seems to be a first generation problem of T2, as the newer (second generation) T2s we are now using do not seem to have this problem with early tests. As well the problem of short ballast lifespan does not exist as it does with the VHO version of T5 lights, but then a VHO version of the T2 does not exist.

Via Aqua new generation Helios VHO fixtures, lamps *VHO Power Compact this stands for “Very High Output”. These come in T-5 thru T-12 standard fluorescent tubes and in the newer power compact (usually 4 pin) lamps such as the popular Current USA, Coralife Quad & New generation Via Aqua Helios VHO .
The new Helios & other VHO Power Compact Fixtures come in a variety of sizes with outputs up to 180 watts out of lamps under 40 inches in length, which rival many Metal Halide (although not in depth penetration). These new higher output VHO fixtures/lamps have higher Kelvin and wattage output than previous generation VHO lamps/fixtures of similar size. These can be used for both marine reef applications as well as freshwater planted aquariums (these new VHOs are not scheduled for full release to the public until early 2009).

Coralife Quad VHO light Coralife has a new quad lamp VHO (such as the 20 inch; 96 watt fixture) that have high output in small space. However both these before mentioned lighting systems are a bit pricy in my opinion for the “light out” for the price paid. As well the electronic ballasts contained in not just these, but ALL these VHO styles of CFL light fixtures (Current USA, JBJ, etc.) tend to have a short life span of under 3-5 years in my experience. When the ballasts go out, generally the replacement cost is the same as a new fixture. With this in mind, I would recommend the SHO Lights which only require an inexpensive incandescent fixture and are vastly less expensive the similar high output PAR light (for example: $35.99 for a 105 watt SHO).

I should also note that as of my latest update of this section (VHO), I have found their durability in relation to cost, and output in essential lighting parameters (not just the way out of date watts per gallon so called rule) is not as good as the up and coming SHO or especially
LED Lights, which in my tests, feedback, research and experience are the future of aquarium lighting, especially as it pertains to freshwater plant and reef aquariums. More bluntly, I would generally advice aquarium keepers to avoid the often over hyped VHO Power Compacts or HO T5 in lieu of the SHO, LED, or Metal Halide for high end lighting needs or stick standard CFL or T2 Aquarium Lights for cost effective aquatic lighting needs.

Compact Fluorescent light bulbs, standard screw in base*PC (or CFL); this stands for “Power Compact” or “Compact Fluorescent Lamp (light)”. These bulbs come in straight pin arrangements, square pin arrangements, and the self ballasted standard incandescent fixture “screw in” type. These bulbs are similar to T-5s and have about the same lumen per watt output (generally around 60 lumens per watt).
standard medium base version of these lamps will fit in a common incandescent light fixture, making these lights about the most economical lights you can purchase with this kind of output. These are an excellent choice for use in planted Freshwater or even Marine

Aquarium Incandescent fixture with 6400 K Compact fluorescent lights Nano Reef tanks under 30 gallons (or even larger aquariums when multiples of these are used), especially when the hood already contains incandescent fixtures, as you need not purchase special fixtures for these. See the picture to the left as an example, please click to enlarge

These self ballasted high PAR lamps are inexpensive and make it hard for even an aquarist on a budget (even a freshwater fish only tank) to not provide the best possible lighting for optimum plant and even fish and Nano reef health!

A newer fixture that incorporates these CFL self ballasted bulbs is the
Eco Light which optimizes the lumens produced with a reflector that I have tested to increase output more than 50% over a the same light without the fixture in a standard aquarium hood.

*SHO Power Compact Lights: A newer Power Compact that in my opinion is awesome for planted aquariums (in fact the best other than some LEDs). As well the SHO can be used for reef aquariums (as an addition to LED or Metal Halide)
SHO Light is currently sold in a self ballasted PC bulbs/light. The 105 Watt SHO Daylight bulb puts out 6300 lumens and is comparable to a 525 watt Standard bulb (click on the picture for a link). This comes out to 60 lumens per watt; however this is a deceptive guide, as you can fit many more of these bulbs in a given space and also utilize more efficient reflectors.

SHO Light, 6400 K Daylight LitThe SHO is already VERY popular with Green Houses/hydroponics and is growing in aquarium use popularity, although it is still relatively unknown to many in the aquarium hobby (although many forward thinking planted FW and some reef keepers are aware of these lights now). In fact the 105 Watt SHOs were in short supply during the spring of 2009 due to just one company purchasing 1000 of these for lighting greenhouses.
My point is; if a company (greenhouse business) that needs the correct lighting at that are price effective to grow plants for a business, all the more reason these should be used in many freshwater plant aquarium applications (& even many reef tanks as well due to high PAR and output needed by zooxanthellae living within corals, complimented by actinic LEDs or MHs).
Keep in mind that there is vastly more research $$$ into horticulture than into aquarium keeping (the money generated by the aquarium industry is just a needle in the haystack compared to most other industries), sadly this point is missed while many continue to use older less efficient, yet often more expensive lighting technology for their planted aquariums.
In fact the medical community is now utilizing these SHO bulbs (& similar full spectrum lights, which is also often making the SHO in short supply) due to increasing studies that show better immune function, mental health, and more. Similar animal studies show like results. I learned of this when inquiring as to why the SHO lights were currently unavailable from the North American distributor, and they pointed out that several hospitals and convalescent homes had purchased over 1500 of these lights (compared to the feeble dozen or so I will often purchase). They pointed out the simplicity of these Super High Output bulbs are quickly making these a favorite of the medical community for their full spectrum light needs (I now use a few 65 Watt 6400K SHOs in my home after learning this and there is certainly a difference). Again as with my previous point with the Greenhouse industry is that the Medical community has far more $ for research and they demand products that are proven to work, unfortunately unlike the Aquarium industry.
See these references:
*New Science Sheds Light on Immune Deficiencies
*Light as a Nutrient

Probably the only draw back is that in any tube light some of the light that shines up from each tube just reflects right back into the tube and is lost (this is called “Restrike”. HOWEVER, the spiral design tends to limit this and based on extreme plant growth achieved this is not as much a factor as some may claim (this is essentially a problem with ALL compact Fluorescent lights).
As well the while the SHO does not produce nearly as much heat as a Metal Halide, the simple fact of the wattage used by these lights still produces heat, so a well vented hood or the use of a reflector is advised (any light should be placed in a ventilated hood/canopy as trapped moisture can quickly damage any light whether an SHO, T5 or LED)

Back to the positives of Super High Output lights; quite bluntly there are few equals for high output aquarium lighting (especially for
planted freshwater aquariums), especially when cost is considered (as well as other positives) since these lamps do not require expensive ballasts like a MH (SHO are self ballasted) and generally cost $30 and up per lamp. Four 85 watt SHOs (or 105 watt for even higher output) can easily handle a 6 foot FW planted aquarium (some T2 or T5 can fill in some more dim spots if necessary), while in Marine Reef Aquariums this same combination (maybe using 105 watt SHOs) along with one or two LED Lights (such as TMC Marine Blue) would work in most reef applications for $500 to $800 for a large aquarium (less for smaller aquariums, or in combination with LED). Consider the 65 Watt SHO for smaller tanks of depths under 15 inches.

SHO lights in twin socket with reflector diagramThe SHO can be mounted into your hood using a standard incandescent fixture. I recommend using an aluminum foil or better an easily made mylar reflector to amplify light downward (& reflect heat away from the canopy). I also recommend venting the hood to remove heat and moisture (a small outward direction fan can be helpful too)
The SHO light is most effective hung as a pendant light using reflector similar to how Metal Halides are commonly installed over an open aquarium. These SHO lamps are also an excellent compliment to MH, VHO or other “strip” lamps for use in reef tanks (in part due to their high intensity in small space and PAR output which is important for the symbiotic coral/algae relationship). Research has shown that many stony corals, clams, and other sessile species that depend on photosynthesis of zooanthellic algae not only thrive but also propagate when maintained under Power Compact lighting alone, and the SHO power compact has a MUCH higher useful light output over standard CFL.

SHO and T8 light comparison The picture to the left was sent in by a client that has a 200 gallon aquarium with four 36 inch/30 watt T8 Aquarium lights and desired correct light to begin growing plants. The top picture shows the clear difference between just one 105 watt SHO and 120 watts worth of 36 inch aquarium lights!
Although this tank is not a marine reef tank nor planted aquarium as yet, it makes a great point as to the output of these lights, despite some of the anecdotal statements made elsewhere on the internet. In fact what is amusing to me is that the only negative comment I have had from someone who actually used a SHO in his 30 Hexagon is that his plants grew TOO FAST and he could not keep up with them due to his work schedule. Honestly this negative is positive proof of these lamps!
Please click the picture to enlarge

In summary as to SHO Lights, as of the most recent update of this section of the article, the SHO is easily one lights of the immediate future for aquarium lighting (the others are the quickly improving
LED aquatic light & T2 and some of the newer T5), in particular planted freshwater aquariums or some reef aquariums. This is not to say that MH or VHO are bad, it is just when consider all the aspects of aquarium lighting parameters (not just the terribly out of date so-called watts per gallon rule), then throw in costs of purchase, reliability (a problem with many VHO & some T5 lights) lower heat output (the main issue with MH); there is simply little comparison at this time.

metal halide, MH aquarium light*Metal Halide (MH); Metal Halide was generally considered the “Kings” of reef aquarium lighting due to depth penetration, output, spectrum, and over all beauty and amount of coral life they help support (however the newest LEDs are now over taking the MH). Aesthetically speaking the Metal Halide is also hard to beat, however the latest technology LED lights are now beginning to surpass MH for Reefs and LEDs have been proven to surpass MH with plant growth in nursery/hydroponics environments (one study/test shows a 12 Watt Full spectrum LED producing better growth than a 175 Watt MH of the same type!).

Even the newer T-5 lamps cannot achieve the depth penetration and overall output of these lights. Metal Halides generally have very good lumens per watt ratio (although I have seen a lot of variation and even incorrect ratings here); however it is safe to say that MH are generally found with lumens to watt ratios of 50 to as high as 90 which is among the highest of any aquarium lights available (along with excellent PAR production as well). Metal Halide work via a gas mixture of halides and other elements, the actual light production comes from the small bubble of gas that is held in place by metal wires and/or supports. The electricity running between them and the small gas bubble, heats them, similar to an incandescent filament. This is one of the reasons that Metal Halide bulbs give off more heat than other bulbs.

Eco Systems Metal Halide lamp and fixture The downside is the heat that MH lights produce, often resulting in the need for hood fans and even chillers, although the newer open design units such as the EcoSystems USHIO double end fixture and HQI bulb works well for 10-25 (or even larger aquariums when other lights are included in the "mix") WITHOUT a chiller.
The sizes I most often have used are between 10,000K and the 14,000K with 75 for small aquariums up to 250 watts for really deep tanks (over 30”). With the 10,000K- 14,000K lamp what I currently recommend.

*LED (light-emitting diode): This aquarium light type uses semiconductor technology as its light source. The difficulty in the past (and where many still misunderstand the complexities of LEDs) is correct wave length of the emitters. For example the infrared emitter uses Gallium arsenide (GaAs) and/or Aluminium gallium arsenide (AlGaAs) for its semiconductor material while Blue (460 nm) uses Zinc selenide (ZnSe), Indium gallium nitride (InGaN), Silicon carbide (SiC), and/or Silicon (Si)
Achieving the correct wavelengths in the correct amounts has been the challenge and why a simple LED flashlight has about as much in common to an advanced aquarium LED as paper glider to an airplane. This however is also the advantage as useless green and yellow light spectrums can be omitted as well.

The new reef compatible & freshwater plants tank LED is likely to take over the market along with the T2, T5, & SHO as they become more readily available, the price comes down and PAR, lumens per watt, & generally aquarium compatibility come up (correct emitter Kelvin technology has been a barrier in the past).
In addition these lights do not have the heat problems, often last 50,000 hours, produce little useless yellow/green spectrum light (in aquarium adjusted configurations), and are very compact. In fact this lack of production of yellow/green light in most all high end emitters used by various LED Kelvin lights (whether 6500K or 14000K) often makes the LED look less bright to the human eye, when in fact the opposite is true as per useful light energy
Please click on the picture to the left for a better view of the one of the newest generation LED light by TMC.

LED lights that utilize the proper Kelvin/Nanometer output emitter bins may prove to be more suitable for aquatic life tank-lighting and reef tanks because they offer superior flexibility when compared with traditional fluorescent lighting & even Metal Halide. When LED lights operate, the photometric radiation remains within a narrow band on the electromagnetic spectrum. Specific photometric wavelengths are often beneficial to some aquatic plant life and reef tanks. Controlling specific wavelengths becomes possible through a basic network of colored LED lights connected to a digital LED controller. The water resistant casing also provides the LED circuitry with adequate protection against moisture and chemicals found within the fish tank or reef tank. Since LEDs emit light only in very specific direction, the installer has the option to illuminate a precise area by simply rotating the polycarbonate tube casing. For this reason the LED does not need to produce as many lumens of light as most conventional lights as many lumens of important light energy is lost due to lack of focus, including all power compacts and fluorescent lights in general, but need higher lumen outputs to achieve the same lighting parameters (one test shows at least a 166% difference of lumens at 20 inches in favor of the Aqua Ray for the same given wattage as compared to a compact Fluorescent).

In tests for plant nurseries (Green House, Hydroponics) full spectrum LEDs such as the TMC Natural Daylight Aquarium Lights or the LED Grow Lights have been proven to surpass even Metal Halide Lights in both growth and useful output.
The graph to the left is the plant growth results comparing the same Kelvin output LED and Metal Halide Lights as measured by a PAR Meter (please click to enlarge view):
It is noteworthy that the human eye is very sensitive to light in the yellow and green regions (500-600 nm). This grapth shows the relative spectral intensity of LED 6500K and a typical HID-MH grow light (6500K), together with the human eye response curve as measured by a PAR meter (for the light output, not the human eye response). This graph also shows why a high performance LED light (of any Kelvin) may not appear as bright to the human eye).

This controlled test has aquatic implications, as photosynthesis is the same whether it be a terrestrial plant, a freshwater aquatic plant, or symbiotic zooanthellic algae found in corals. The only difference would be that light energy is quickly absorbed by water, especially red light waves and many MH (such as a 14,000K or 20,000) have excellent depth penetration, however modern LED lights such as an AquaRay/AquaBeam 500 Marine Blue have similar penetration.
It is still easy to make assumptions from the raw data based on this study with plants that a 12 Watt LED can at least replace a 100 watt MH of equal Kelvin ratings in reef or planted aquarium applications (the
TMC AquaBeam Ultra 1000; 30 Watt LED should easily replace one 175 Watt Metal Halide (if not a 250 MH) of similar rating for marine applications).

Metal Halide comparison with LED LightsThe picture to the left shows the useful PAR light energy of a MH compared to a LED Light (both full spectrum daylight).

*Dark Blue = LED Lights (6500K)
*Light Blue = Necessary PAR Spectrum of Chlorophyll
*Lavender = Metal Halide (6500K).

There are mixed reviews on the older generation larger units such as the Solaris (which is basically the first generation of LED aquarium lights & quite pricey at that) that replace the MH.
However the newer 3rd generation and lower cost
TMC Aqua Ray are a vast improvement in price/affordability and PAR output; in fact at the price of the AquaRay LED Aquarium Light Strip, coupled with the 50,000 hour lifespan their actual light cost per hour for comparable output is actually favorable to most available aquarium lights.

More about emitters: Many do not seem to understand that not all emitters equal, even with the Cree-XR-E emitters sold commonly for other applications (these are an excellent emitter in terms of lumen per watt output) are only as good as their correct wavelength output (Kelvin Temperature/Nanometers). I have used and tested many “cheap” emitters or even otherwise good emitters that do not produce the important light energy needed to support aquarium life.
For instance, exclusive Cree Emitter bins used by Tropic Marine Center AquaRay/AquaBeam should not be confused with Cree emitters sold for other lighting applications, as these do not produce the correct Kelvin/Nanometers of Light required for delicate marine reef and freshwater inhabitants and plants. Just one example is the actinic emitter bin used by TMC produces a rather exact 465nm - 485nm (which as per our PAR section of this article is the primary UVA wavelength for optimum PAR) vs. the often more broad and lower (420nm) of many other lights.
Think about why a CFL 10,000K daylight is so much different and more expensive than a common household CFL sold in hardware stores, or the many decorative LED aquarium lights or even those for home or flashlight use; try using one of these to grow your delicate coral or plants (the answer is they will not). Sadly shortly before writing this update, I got a obscene email about why should he pay for a Cree emitter in a high end aquarium light such as the Aqua Ray or similar, when he could by these for much less money for other application. This shows the unfortunate lack of understanding of what is important in aquarium lighting, whether LED or other lights (hopefully this is understood better for any reader here up to this point in the article). This is the reason most earlier LED aquarium lights were not adequate for supporting life properly until recently.

Use of LED to prevent Red Slime
Another positive attribute of LED Aquarium lights as per s recent study (August of 2009) is that LED used in marine aquariums that suffer with
Marine Red Slime Algae (Cyanobacteria) can immediately eradicate Red Slime algae when used in a full spectrum lighting configuration. These “immediate” results were just two weeks all the while other lighting configurations (such as switching to 6400 K CFL from 10,000K CFL) show slight improvement, the LED lights showed much more dramatic results. I do not know (as of this update) the exact reasons, but my suspicions is that CFL (including VHO & SHO) still produce more of the yellow/green nanometer range of light which encourages Cyanobacteria and discourages more discourage competing green algae.

More LED information
The flaws of LED aquarium lights are quickly disappearing and based on the energy savings in electricity in wattage of the lights (as compared to MH) as well as electricity use for air conditioning or the cost of a chiller often necessitated by larger Metal Halides. I should also note that LED light technology is growing by “leaps and bounds” and many of the bugs including price are currently being improved upon.
 New generation TMC AquaBeam 1000 LED light IN FACT Tropic Marine Center has a new Reef capable LED (with vastly higher lumens per watt & improved PAR) that is currently being tested by some friends of mine in the professional aquarium keeping business and the price is also improved over older LED fixtures such as the Solaris as well.
Aqua Ray has vastly better price and is improved in its PAR, especially if your purchase the Reef White versions or Natural Daylight.

Another newer (& capable) LED is the Current Power Brite LED light strip & Maxspect Aquarium LED G2.
However the Current USA is more of a marginal LED for Reef or planted freshwater aquarium use and although about ½ the cost of the Aqua Ray, its output is about ¼ that of the Aqua Ray (the Aqua Ray has 5 x 2.4 watt higher output emitters as compared to 4 x 1 watt emitters for the Power Brite), making the Power Brite a poor value when compared apples to apples. That said, the Current LED is still an improvement in many ways over earlier generation LED aquarium lights.
The Maxspect Aquarium LED G2 is a more capable aquarium LED, although the Semi LED chips are not to the standard of the patented CREE emitter bins used by the TMC in focused lumens and PAR output per watt, however these LEDs make up for this in sheer wattage (& price too though). It should be further noted that the Semi LED emitters are licensed by Cree, and this license is for previous (older) patents

As well many other LED lights now on the market such as the Rio Mini Sun, Marineland Double Bright, or “Ecoxotic Stunner” are only for adding highlights and supplemental lighting, not as a primary lighting source. This also is the case for the many submersible LED lights that are also available in stores or the internet.

LED Light systems are easily complimented with T5 Fixtures,
T2 fixtures for smaller applications, or even the SHO self ballasted high output CFL for large tank applications (please note that the SHO are currently only available in daylight bulbs). See the picture to the above for an Aquarium with a Marine Blue Aqua Ray LED Lighting system placed over it

*PAR LED Lights are another newer innovation. These high PAR 6500K LED lights come in many different configurations of varying number of emitters.
This LED was originally developed for the Hydroponics/ Plant Nursery Industry but has now crossed over for aquarium use. This LED produces very high amounts of useful lumens in the peak PAR with almost no wasted yellow or green light, making this an excellent and more economical choice for planted freshwater aquariums (& even marine aquariums to, especially those under 24 inches.
This light is very focused with little spread, making it idea for intense bright spots, but less than ideal for lighting vast areas of an aquarium. The other unique feature is this light is simple to install via a common household incandescent fixture.

*As well TMC has a now third generation AquaBeam/ AquaRay that has the one of the latest Generation
CREE XR-E Power LED emitters and new wide angle beams. These 3rd generation Aquarium LED are available in multiple configurations from all blue emitters to the Natural Daylight that are perfect for planted freshwater aquariums. As well they are just one more step forward in LED technology that makes these light fixtures even more of a no brainer for higher end aquarium keepers that are looking for long term results and even value.
TMC is now testing the latest offering by Cree, the XP-G emitter. However, this emitter is only available in a 9000K wide angle emitter and will be placed in their newest offering; the AquaBeam 1500 XG (when available).
I now have an AquaBeam 1500 XG and am testing this new LED fixture. Early tests (including a PAR meter) confirm what have been told that this new emitter is meant more for widespread illumination and is more a replacement/alternative for the AquaBeam 500 than the 1000 models which provided almost double the PAR at the same distance (12” and 24” tests), making this a nice LED light for widespread aquarium light distribution from a small fixture footprint (but not a replacement for the Ultra 1000s or especially for a 400 Watt Metal Halide for deeper aquariums)

*LED Summary; The bottom line is when you compare a LED Aquarium light to the many popular CFLs and even T5s in terms of lumens per watt, focused lumens, lower wasted yellow/green light energy, low heat output, energy consumption, long life (50,000 hours vs. 8000 hours), the modern LED is generally a better light even in long term cost since (as an example) a 12 Watt Aqua Ray Natural Daylight can easily replace a 36 Watt power compact (also daylight) when you compare ALL aspects of lighting as presented in this article.
When compared to even older T8/T12 aquarium lights, a third generation TMC Aqua Ray requires only 17% (or less) of the wattage for the required light energy of a planted or reef aquarium.

Here is a video comparison between this new Programmable LED and a more common 72 watt 10,000K light fixture:
LED Comparison with Fluorescent light

Lunar (Moonlights)

Often LED as noted above are used as lunar or moonlights. This is an area where anecdotal information seems to be the main information available.
This includes the common belief that moonlight should be “blue” when in truth all the moon does is reflect diffused sunlight back to the earth (more during full moons, less during other phases). Dust or moisture can affect the color spectrum seen by the human eye as well (which often makes the light appear blue).
This means that a dimmed/diffused daylight is a more accurate production of moonlight. This can be done by fading a Reef White AquaBeam LED as an example.
Essentially these are very popular for marine reef aquariums for both a low level “night light” and for simulating moonlight for corals and coral propagation.

Where some of the misinformation comes into play is that many will state that fish need these lights, of which there absolutely no scientific proof and also that corals need these for proper growth which also has no scientific evidence to back this up. Aquarium Moon lights (lunar lights) do nothing to aid in this.

Lunar cycle animation for aquarium What lunar lights (moonlights) could do with correct programming for the marine reef aquarium is to simulate marine lunar cycles which are necessary for some fish and coral reproduction/propagation, as Corals in the Great Barrier reef spawn 3-7 days following the first 2 Full moons in late spring and early summer. Even here there is still a lot of controversy as to what cycle is best and how much light is best.
From what I personally have observed combined with the opinions of other aquarium professionals is the use of gray nylon filter placed over standard daylights (T2, T5, T8 CFL, etc.) can work as a moonlight; even low level “white” lights such as nightlight bulbs, or even the
Rio Mini Sun LED lights can work just fine for this since this has shown to be a more of a low level light issue and timing issue.
Adding or subtracting the amount/intensity seems to be the secret of simulating these cycles which can be accomplish easily either manually or with electronic timers (that can be set to more accurate monthly 29.5 day lunar cycles of lighting). Strategically placing these lights also shows evidence as to properly simulating this effect.
Please click on the picture above/left for a larger animated version of the lunar cycle

If anyone reading this article has good scientific evidence to the contrary (or even to support) what I have just said about the use of lunar lights, please email me on my contact page with these references.

Induction Lighting

Induction Lighting, how it worksAlthough not a new technology per say, it is new in regards to commercial availability as until recently, new developments have broken down the barriers of costs and technological setbacks, such as EMC interference, lumen depreciation, ability to dim and a useful range of available wattages.
This type of lighting last up to 100,000 hours (often over 20 plus years under normal usage) and is another good candidate to replace Metal Halide Lights. Induction lights do not have the warm up times of MH or similar (20 second warm up vs. 10 minute warm up), use no mercury, have no filaments to burn out, and they produce half the heat (160 F vs. 300 F for a 200 watt Induction Fixture vs. a comparable in output 400 watt MH fixture).
Induction Lights generally have a high CRI of 82 with a high lumen per watt output (surpassing most MH).
Currently the main negative as per Aquarium use is that Induction lighting is only available in 5000 K Daylight vs. a better 5500-6700 K Daylight, although this is still a viable Kelvin temperature as per PAR especially when one considers the high output delivered with half the heat output.
Hopefully the companies that are making these lights will see a market in the Aquarium industry and make them in models that provide the correct PAR needed by corals and plants as these can be a nice rival to the Metal Halide, LED, and SHO!

HID Xenon

HID stands for “High Intensity Discharge”, this technology is currently used in high end luxury cars, however there may be aquatic implications here in the future as PAR and other potential issues are worked out. HID lights use an electrical charge to ignite xenon gas (a colorless, heavy, odorless noble gas, which occurs in the Earth's atmosphere in trace amounts) contained in a sealed bulb. The technology of HID automotive lamps is similar to that of common vapor-filled mercury vapor street lamps.
These Xenon HID lights seem to produce much in the lower chlorophyll A segment of PAR, but currently not as much in the higher infrared part of PAR

Important Parameters to consider when choosing a light for your aquarium (not a complete list):

• Watts per gallon,
• Lumens per watt,
• Lumen focus
• PAR (often easiest determined by Kelvin output),
• Useful Light Energy (not wasted in yellow/green light spectrum that green plants and zooanthellic algae reflect)
• Output in relation to bulb length (this is where LEDs and to a lesser extent T2s and T5s excel).
• Lux, I generally only consider this parameter in deeper Reef and occasionally deeper planted freshwater aquarium to determine if I am getting the proper light where it needs to be.

The watts per gallon is part of the lighting equation as stated above is highly inaccurate when taken by itself, yet may in the aquarium hobby industry still go by this outdated generalization which leads me scratching my head with all the advances in lighting technology. Taken together, the first FIVE points are the most critical (which does include watts per gallon), but no one of these should be a sole determiner of the lights.

As an example of the inaccuracy of the watts per gallon so-called rule, please consider these comparisons for an assumed 25 gallon aquarium:
* 20 watt T12 light with a Kelvin temperature of 5000 K,
Compared to a:
*20 Watt
LED with an adjusted Kelvin temperature of 6500 K.

So assuming you would like 4 watts per gallon (this “rule” came about when T12 & T8 were the most common lights), you would need five of the described 20 watt T12 lights.
HOWEVER, once the other important factors are applied the described LED is shown to require vastly less wattage to produce similar results than the T8/T12 bulbs.
*PAR; the LED is more than 25% higher, as well many current LED emitters designed for aquarium and plants are more than 50% higher.
As well the useful light energy adds at least another 25% for an increase of 50% in this area of light output
*Focused Lumens; the LED 166% more efficient in focused lumens (about a 2/3 reduction of necessary watts)
*Lumens per Watt; the LED is double the lumens per watt.

In a rough math equation using a starting point of 100% of the T8/T12;
100 less 75%= 25% less 67% (2/3) = 8.25% less 50%= 4%
In other words you would need 4% of the wattage to provide the same lighting as similar watt fluorescent aquarium light
This would roughly result in just one (actually less, and you will still have more light) of these lights for the same tank size (a 25 gallon in this example).

As you can see the watts per gallon rule falls apart in this comparison, in fact in this comparison one watt of high output emitter LED has a higher output of usable light than the 25 watts of the T12 (100 divided by 4). Of coarse the differences can vary, so even this comparison only works for the described lights and tank, this is also based on the newer Cree XR-E Power LED emitters employed by TMC (and some PAR 38 LEDs) which have a high output of useful energy.
In fact based on raw data from controlled tests, even the modern comparable Kelvin HO T5 lights or Metal Halide which are so popular do not hold up in comparison to a modern LED with the Third Generation AquaRay LED emitters. This data indicates that a modern LED requires 14-28% of wattage for the same useful light energy output.
Even then a T5 or even more so a
T2 are vastly superior to the older style aquarium lights when all criteria are applied (SHO as well are also superior).

Changing bulbs:
With the exception of LED, most aquarium bulbs go through what is called a half life whereby they are at 50% output. This generally happens around 6 to 9 months in time with normal usage however with lower usage (say 8-10 hours per day) this can be stretched to 12 months.

Lighting Time
Here is a summary of lighting requirements for different aquarium types. I recommend timers for any aquarium to provide good daylight/night cycles, however this is even more important with Planted Freshwater and Saltwater Reef or Nano Reef tanks. Turn the actinic lights on about one to 1/2 hour ahead of the daylight bulbs and one to 1/2 hour later in the evening. I generally have the brightest lights on for about 12 hours per day. Sometime with MH I will have them in a third cycle that is on for only abut 10 hours or less. I would run moonlights for about 14-16 hours (some prefer to run these 24/7, however I have yet to find in benefit from this that can be scientifically proven other than aesthetics).

Light (lamp) placement:

Pendant vs. Canopy with Reflector (Mirror, Aluminum, Mylar)

The advantage to a pendant reflector over a canopy with a reflector (mirror, aluminum or mylar reflector) is that it will radiant downward in a slightly more magnified fashion than a reflector, however the reflector/mirror has one advantage over the pendant and that is more wide spread light distribution. A pendent (such as an SHO or Metal Halide) or LEDs hung on rails over an aquarium allows for an open tank which allows for more light energy to reach the tank. The negative is evaporation and possibly aesthetics (which of coarse comes down to opinion).

If lights are placed in a canopy (which in my opinion looks better) it is generally best to keep a lid on the tank to prevent too much moisture from building up inside the canopy which can also damage lights. I recommend venting the canopy and adding a small fan in at least one of the vents aimed to push air out will help both cool the inside of the canopy/hood and just as importantly help expel moisture. With low heat lights such as LED and T2s, this is of less importance especially for heat, but still helps protect lights from moisture damage.
The use of a reflector such as mylar (even heavy aluminum foil can work, although it tends to degrade from salty moisture over time in my experience) protects the canopy wood from heat and is useful for directing light downward, especially if SHO or Compact Fluorescent lights are used. BTW, my first choice is Mylar for both reflective properties and longevity. Please the picture in the T2 Light section of this article for a canopy using Mylar (see this website as one many sources for Mylar;

The use of lids (glass in particular) does block light energy and gets buildup quite quickly under the lids (although lights exposed to open tanks need to wiped clean often too), however the choice of lid can minimize energy loss (see the section lower in the article under Marine Light Summary for more about lid choices)

So this choice comes down more to aesthetics, space, personal preferences, tank arrangement of plants or corals and more.

Light Penetration

What is often a bigger issue, especially with deep tanks (over 24 inches) is to allow as much of the blue light (which is found as part of the light spectrum of high PAR Daylight 6400 K lights) as possible through to the tank and often a glass top will block these light rays (over 60%) so using polycarbonate or no lid at all may do more for effectiveness than whether you use a mirror or pendent (see further in this article for more on this subject).
As well for tanks over 24 inches the use of some higher Kelvin in your light “mix” may be necessary for coral tanks or in some cases high light requiring plant tanks (depending upon the environment being replicated, as a high tannin, often shaded Amazon River tanks would not require the light intensity and higher Kelvin output of a Reef Tank).
The use of 14,000 K MH (or even higher Kelvin 20,000K MH) or
AquaBeam Ultra 1000 Reef White LED in a mix with High PAR 6400 K SHO lights may provide the “mix” necessary for deeper tanks. Even in tanks under 24 inches, the use of actinic blue lights may help provide the correct PAR to specimens lower in your tanks water column; a LED Reef Blue 50,000K may help provide this (this LED along with the Marine Blue is also excellent deeper tank penetration) .

Here is the general light spectrum absorption of water:
• Only 73% of the surface light reaches a depth of 1 centimeter (less than a half inch)
• Only 44.5% of the surface light reaches a depth of 1 meter (3.3 feet)

Specimen Placement
This is an important consideration that is often missed or not enough weight is given to this part of aquarium lighting and aquascaping

Reef: Another important point that is often missed by many reef keepers (usually newbies) is even with newer technology high output lights (such as a MH, LED, HO T5, T2, or SHO), specimen placement can make or break a good light system.

As per the previous section as to general light absorption of water, I would move corals as high up in the water column as possible, this especially important with SPS corals (short polyp stony corals) where placement on the rocks directly under your lights is even more essential. This is not as essential with LPS corals (long polyp stony corals) since they are more commonly found in near the sandy lagoon bottoms.

Sometimes in conversations with reef enthusiasts that are questioning different lighting systems/ideas is that it is often missed that the most high light requiring corals (such as SPS) do not grow 100 feet (30 meters) below the surface in the reefs and that these corals will be just below the surface, so regardless of the lights you choose, placement is extremely important. Even less light demanding tropical reef building corals species are restricted to the euphotic zone, the region in the ocean where light penetrates to a depth of approximately 230 feet or 70 meters (there are cold water corals that grow in deeper water, however these are not the reef building corals kept in aquariums that secrete calcium carbonate).
I should also note that with SPS corals in my own experience, that placement low or even in substrate that I have observed the corals getting “eaten away” by bacteria from the bottom up; while this is an anecdotal observation of mine (as other factors were not tested in a controlled scientific study), it is still consideration in coral specimen placement.
The bottom line is that you can have the best lighting system that money can buy, but poor placement of specimens can make it all for not.

Another thought as marine tanks in general, is to consider what type of environment you attempting to duplicate; for instance a Reef Tank set up to duplicate the Great Barrier Reef would require aquascaping and higher power lighting to best replicate this environment. While a marine tank set up to replicate the much more turbid waters off the California coast would not require the same aquascaping or as high power of lighting.

Freshwater: If your lights are for
Freshwater plants I would move the high light requiring plants directly under the lights (I generally elevate them with terracing, which can look quite attractive if done well and serve a dual purpose of aesthetics and better light energy absorption).

As with marine tanks, consider the environment you are replicating; for instance an Amazon River environment aquarium (with fish such as Discus) are full of tannins and have many shady areas and so one cannot compare the lighting needs of a tropical reef with the Amazon River. More light and dark spots should be utilized so as to provide amore natural and comfortable environment for your aquarium inhabitants, as well the same intense lighting for the same size Tropical Reef tank should not be used for an Amazon River aquarium of the same size and depth.

Please note that I have received many requests for exact recommendations of lights for certain aquariums. I prefer to not give these as there are too many variables which then will make my advice anecdotal, as with Aquarium Medications, Chemistry, & similar subjects I prefer to give as many tools for the aquarium keeper to make an educated decision on his/her own. As well since Lighting is a fast changing part of aquarium keeping, a recommendation I make today may be less accurate in a year (or less).
As a guide I will make a few suggestions in the following sections, however please take these as suggestions, not something written in stone. Please consider all I have written up to this point, your personal aquarium parameters, inhabitants, budget (which is always important), & more when deciding what lighting systems or combinations there of to use.

Penn Plax Aquarilux aquarium lights • A BASIC FRESHWATER FISH TANK (including some low light plants) tank MAY not need as much lighting and will often do OK with one “Aqua Glo”, “Color Max” or similar (30 watt) light for a 60 gallon aquarium.
6400 K Power Compact is also an excellent basic freshwater and inexpensive tank lamp. Please keep in mind that even though “Aqua Glo” and “Color Max” produce some PAR, they do not have the output (lumens per watt, lux) for any thing more than low light plants. Other basic T8 & T12 aquarium lights worth considering that are also reasonable good lights are the ZooMed and Coralife Trichromatic as well as the ZooMed FloraSun and VitaLite. There are many others that have reasonable outputs in the 5500-8000 Kelvin range.

It is worth noting for even a basic freshwater aquarium that better lighting will usually result in healthier fish and easier control of algae, especially Brown Diatom Algae. Higher PAR lights may have an effect on
Redox which directly impacts fish health, absorption of nutrients, and general disease resistance of fish
Unfortunately for many basic freshwater aquarium hobbyists, commonly sold aquarium bulbs do not publish anything other than “aquarium light for that brings out fish color”.

Besides the before mentioned Power Compact lights, the
T2 lights are excellent lights that have good PAR for health, plant growth, less Brown Algae. These can also be linked for larger aquariums which makes for a one size fits all first rate fixture (pictured to the left).
Please AVOID the incandescent standard aquarium light that are unfortunately still sold in many aquarium supply retailers (please consider substituting CFL lamps mentioned earlier in these fixtures!)

*As an example, with a 36”L x 15”W x 16”H 40 gallon aquarium I would suggest (2) 11 Watt 6400K (or even only one 13 watt) T2 Lights as a good set up for a basic freshwater aquarium.

For further basic freshwater tank lighting information, please see this article (in the Light Basics section):
“Freshwater Aquarium Basics, Care”

• A FRESHWATER PLANT aquarium needs a higher PAR plus more lumens/watts of light. Photosynthesis takes place at the blue end and especially at the red end of the Nanometer curve (420 nm blue and 670 nm red). This area of peak photosynthesis is referred to as “PAR” as discussed earlier.

In aquariums where you cannot or do not want to have multiple bulbs, an approximately 6500 K bulb works best most planted tanks (tanks deeper than 30 inches may need higher Kelvin outputs, however this will also sacrifice some of the high percentage of PAR found in a 6500K daylight).

In smaller aquariums I now tend to use the economical Power Compacts with 6400-6700 K Daylight (which tend to be full spectrum as far as green plant growth is concerned) and occasionally actinic combinations. An excellent bulb for low to some medium light requiring planted tanks and that will fit in a standard socket is the
6400K, 13 watt Fluorescent Daylight bulb for aquariums or the Eco Light complete CFL clamp fixture (pictured to the left). This is a great economy/starter plant and fish light; this bulb fits any standard incandescent fixture and is an inexpensive way to turn an incandescent hood into a power compact light fixture useful for plant growth in small aquariums!
For a step up in smaller tanks, the T5 and especially the T2 in 6000 to 7000 K range are good choices. The T2 Fixtures (pictured to the left) can be mounted in a hood, placed on or above an aquarium, attached end to end to make a long fixture or overlapped, making these about the most versatile plant capable (or Nano Reef) fixture available today. For tanks as large as 75-100 gallons (a minimum of four 13 watt/20 inch T2s would be required for planted tanks this large).

For larger Aquariums (over 60 gallons) I recommend the newer
SHO (Super High Output) 6400K Bulbs, high output lamps. Quite bluntly I have not seen a better plant light as of writing this (which is why they are also popular in Greenhouse/Hydroponics use).

The “new generation”
LED Aquarium Lights which can be purchased in Natural Daylight Configurations for high end, long life, low energy applications are unmatched in output/growth versus power consumption. The PAR 38 6500K Spotlight LED can also be used high light areas.

Since plants use both green and red light for growth, the use of either full spectrum daylights are useful for healthy green plant growth. I have seen it mentioned & observed that blue actinic light will encourage certain algae growth. The blue light encourages all green growth, both plant and algae, so if the plants can out compete algae based on other parameters this generally is not an issue.
I have observed (as well as heard from others) that Black Beard Algae (BBA) is more common in tanks where actinic lights are employed, admittedly this is by non scientific observation, but I would consider using only 6000 to 7000 K lights if this is a concern

Incandescent bulbs have a high infrared output and do well with plants, but also put out a lot of undesirable heat and tend to more in the wasted energy yellow spectrum as well (not to mention a 85 watt standard inc. bulb does not even come close to comparing to a
85 Watt 6400 K SHO Bulb in output even though they are of the same wattage). Cool white fluorescent bulbs are not recommended in any aquarium as they only put out visible light (around 550 NM/ 4200K) and not the spectrum needed by plants or even fish (warm white are even worse @ 3000K).
Keep in mind the light requirements of the plants you are keeping. As stated above, watts per gallon is not the only rule to follow for aquarium plant requirements. Know your plants and know your lights then loosely apply this rule.

A final note as to freshwater plants, is that the more light (in correct PAR) you add, even in low light plants, the more the plants will require additional nutrients; in particular carbon. This can be provided by fish respiration, products such as Flourish Excel and CO2 generators, however in medium to high light plants you will likely need to supplement CO2 in some form or another.
Please read this freshwater aquarium plants article for much more about this subject:
“Planted Aquariums”

*As an example, with a 36”L x 15”W x 16”H 40 gallon aquarium I would suggest (2) 13 Watt 6400K T2 Lights as a good set up for a low/medium light planted aquarium, Or (2) 65 Watt SHO or (2) Natural Daylight TMC LED lights for a high light planted aquarium (of coarse combinations of lights and other variables apply)

*Please note that as of the most recent update, the SHO is still my preferred light for high light requiring planted tanks over much over 60 gallons due to the shear output of usable light energy in a relatively small space (as well as based on results in the indoor horticulture industry). However these lights do not fit as well into low hoods as would a LED, PAR 38 LEDs, T2, or T5 and although they do not require fans, good hood ventilation is also important. The SHO also requires a little more DIY ability as well.

• A BASIC SALTWATER or FOWLR tank also does not have as high of requirements, as but more than freshwater (especially if you do not want too much brown algae). A “Coralife 10,000 K” or “Hagen Power Glo” are reasonable (but very outdated) basic saltwater lights.
T2 Fixtures are an excellent “step up” from basic with vastly higher output per watt. The newer Newest Generation T2 Fixtures are an excellent choice for smaller aquariums or even larger aquariums when the T2 fixtures are connected together.

For smaller tanks the
6400 K CFL lights make a good choice and the SHO for larger aquariums.
Finally and although pricey, an LED is still worth considering especially when you consider the 50,000 hour life, and high usable light energy output.
Recent research in humans can also be extrapolated to fish only tanks that shows good lighting can improve health and increase disease resistance; for this reason a T2, SHO, or LED are worth considering over a1980s style “Marine Glo” T12/T8 light

*As an example, with a 36”L x 15”W x 16”H 40 gallon basic marine aquarium I would suggest (2) 13 Watt 6400K T2 Lights, or (2) 13 Watt 6400K and (1) Blue T2 Light as a good set up (other combinations of lights and other variables apply).
One TMC AquaBeam Reef White, Marine White or Marine Blue can easily light a 40 gallon fish only/FOWLR marine aquarium as another alternative.

• A BASIC REEF OR NANO REEF: In a 10 gallon Nano Reef, two
Power Compact bulbs will usually do well especially if used with a new high output T2 lamp.
The new 6400K, Actinic T-2 Lamps/Fixtures are good compliment to a Pico or Nano Reef due to their compact size and high lumens per watt output and our now my choice for these tanks along with TMC or similar HO LEDs.
These fixtures can also be mounted in parallel and/or snapped together end to end for larger aquariums with higher output needs.

Other considerations especially larger basic reef tanks are a
VHO Light or even a 65-105 watt SHO bulb.

Finally the VERY new
AquaRay LED Light systems can be used alone or in combination with T2 or T5, CFL or possibly SHO lamps for Basic Reef or Nano Reef Tanks. Generally I recommend the Aqua Ray combined with the T2 6400 and/or Blue fixtures in tanks under 60-75 gallons (or even larger if linked) or the T5s for larger tanks.

*As an example, with a 36”L x 15”W x 16”H 40 gallon aquarium I would suggest (2) Reef White TMC LED lights or (2) 6400 T2 & (1 or 2) Marine Blue TMC LED for a basic reef aquarium (of coarse combinations of lights and other variables apply)
*Another example with a 60 gallon hex aquarium, I would suggest the more compact
TMC AquaBeam 1000 with more than double the output of the TMC AquaRay/Beam Strips in a more compact space (for longer tanks, the LED strips are generally still more practical)

• AN ADVANCED REEF with hard corals (photosynthetic corals which obtain their primary source of energy from light and then also actively feed to obtain more energy) may need a several or a combination thereof Metal Halide and
Marine Reef LED, SHO, T2, T5, or CFL bulbs.

TMC Reef White, Marine White and Marine Blue AquaBeam 500 LEDs (even the Natural Daylight LED), along with the AquaBeam Ultra 1000s (for even more intense bright spots, similar to that of a 250 Watt 14,000-20,000K Metal Halide) would make for an excellent high end application; with two T2 Lights being substituted to keep initial costs down in Reef tanks with slightly less light demanding coral inhabitants.

In a large Advanced reef aquarium combinations of lighting systems may yield your best results and also possibly alleviate the need for expensive and often unreliable chillers.
For example in an 8 foot 200 plus gallon advanced reef tank 4-6
AquaBeam Reef White 500 LED and Marine or Reef Blue LED & 3-4 AquaBeam Ultra 1000 over the most light sensitive clams and sps corals. T2s or T5 light strips could be substituted at about 2 to 1 for the AquaBeam 500s

Another possible lighting arrangement is the use of about four 85 or 105 SHO lamps mixed with a couple Reef White 500 LEDs or Marine or Reef Blue LED and a AquaBeam Ultra 1000 or Metal Halide over the most sensitive corals. With this configuration, the best way to install the SHO light is suspended over the aquarium them in a slightly staggered parallel (utilizing the SHO reflector for this application would be optimum).

Of course for energy and heat saving the use of all LED Aquarium lights is now a reasonable option due to lower costs of purchase, much higher useful energy output, and long life (50,000 hours vs. 8000-10,000 hours of other lights)

Marine Lighting Summary;

I will point out that there is no one way to best light a marine aquarium, so my apologies for the multiple suggestions that may leave some scratching their heads wondering if there is one best lighting system for marine aquariums (especially reef). The answer is unfortunately NO!
However please do not get caught up in 20 year old plus anecdotal reef keeping light suggestions that are not based on modern technology or scientific facts as to the needs of high light requiring reef inhabitants. Most of the old school lines of thought are still stuck on the severely out of date “watts per gallon” rule which when applied to modern LED, T2, T5, & SHO lights is extremely inaccurate.
With the modern LED Light Technology, and often ignored SHO, the T5 and the T5s newer more compact (& higher lumen per watt output); the T2; one has many excellent choices

• IMPORTANT- Another point about lighting in general is that higher wave lengths of light such as UVA do not penetrate glass well or even acrylic. I recommend direct lighting (best), quartz or polycarbonate where UVA is essential. Just make sure to clean your bulbs or polycarbonate tops regularly to prevent build up that will block light.
Even though infrared will penetrate glass, it will not penetrate dirty glass with algae or hard water deposits on it, so keep your aquarium cover clean for any tank where lighting is important such as FW plants or Reef Aquariums.
Here is a very basic breakdown of UV blocking potential:
*Glass- about 60% of UV will be blocked
*Acrylic- about 40%
*Polycarbonate- about 8-10% (this is what I used when a lid was necessary)
*Quartz- about .5-2%


Remember from all the information written above, that when deciding what lighting to get for your aquarium that the watts used is only one third or less of the equation in deciding what lights, what size and how many should be used. I will admit that I still will use the watts per gallon a starting point, but I do NOT finish with this either; this would be like starting a race in first gear and never shifting gears the entire race!

Please note that besides years of personal fresh and saltwater keeping experience, MUCH more of this information I have written here comes from research comes from OUTSIDE the aquarium industry as way to much aquarium lighting information commonly found elsewhere is just the same regurgitated information that just gets passed around in a small circle within the industry and hobby. Much of what I have learned (and I am STILL learning) comes from this constant research of as many lighting tech research as I can read often from horticulture or other outside sources as noted earlier
Some examples include the lack of information about SHO or T2 bulbs that are often superior to more commonly recommended bulbs in the aquarium hobby, yet in much better funded lighting and horticultural industry literature these bulbs are much better known.

There is also good evidence that correct lighting benefits ALL fish as well, including salt & freshwater fish. I have observed better disease resistance in marine fish in loosely controlled studies when lighting is upgraded to higher intensity, high PAR lights. Proper lighting may play a role in nutrient assimilation, improved
Redox, lower incidence of Brown Diatom Algae. Studies in humans that show an impact of lighting on health, may have strong implications for fish (this may be a factor in my studies that showed higher disease resistance when lighting is improved).
Lighting that as closely duplicates the sun (not necessarily is most pleasing to us) is important for ALL life, although more noticeably for corals and plants, but fish too are part of this chain of life. Basically if you take away the sun and the energy it provides, you take away life itself and I do not think if you are trying to achieve the best environment for your fish whether fresh or saltwater, you are doing them a favor by depriving of this source of energy, so duplicating this is one more part of your “aquarium keeping puzzle” (see
“Aquarium Disease Prevention”).
I should point out that obviously, some fish prefer subdued light, but this is easily handled by hiding places, caves, plants (live or artificial), products such as Peat or
Indian Almond Leaves that “color” the water, and simple placement of lights where as some areas of the aquarium are better lit than others with plants/corals placed in way that benefit the most in these areas.