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Water Temperature, Chemistry and Flow

Generally speaking, our goal is to manage in a relatively small closed system,  a stable environment that mimics the natural environment (a very large, open system) of the animals and plants we are keeping -- think, Great Barrier Reef.  Note though that wide variations appear to all "work" successfully.



Start fresh:

In the absence of safe and reliable natural saltwater (NSW), we have to make our own.  Because most tap water has all kinds of "stuff" harmful to a closed saltwater reef system, we start with pure fresh water and build from there.

The most popular approach is to use an RO or RO/DI system to make pure freshwater in a food grade plastic container.  Then, add-in a commercial mix to get the desired saltwater with the required chemical components.

We use this artificial saltwater (ASW) to start the system and for periodic water changes.



Temperature:
80°F (if we had to pick one)
Acceptable range: 72-84°F
The debate continues. Note that there are videos online of delicate (so "they" say) acros totally out of the water at low tide on a daily basis baking in the mid-day sun. Doesn't sound so stable to us.

Water Movement and Flow:
General rule is a minimum of 10x your tank volume per hour.
For high flow animals like SPS corals, consider up to 20x.
The water needs to be moving within the display tank, and through the sump (the water treatment and filtration area) and back again. How, when, where, and how much depends somewhat on the animals. 3-5 times your display volume per hour through your sump is more than sufficient for filtration purposes. Flow and movement can be achieved from a combination of the return pump and devices (pumps, wavemakers, propellers) placed directly in the display tank. 

On a natural reef, there is a gentle flow around the coral head every two to three seconds. Every 10 seconds there is a second much stronger surge. Lastly, tidal flow moves unidirectionally twice a day.

Chemistry:
Debates here also.

Salinity
FOWLR: 1.020
Reef: 1.025

pH
subject to change between collection and testing; can be done accurately and inexpensively at home
FOWLR: 7.6 to 8.4
REEF: 8.0 to 8.4

Ammonia (NH3-4)
Natural Seawater Value: 0.010 mg/L
Acceptable Range: 0.000 to 0.050 mg/L

Nitrite (NO2)
Natural Seawater Value: 0.010 mg/L
Acceptable Range: 0.000 to 0.100 mg/L

Nitrate (NO3)
Natural Seawater Value: 0.050 mg/L
Acceptable Range: 0.000 to 25 mg/L

Phosphate (PO4)
Natural Seawater Value: 0.030 mg/L
Acceptable Range: 0.000 to 0.250 mg/L

Silica (SiO2-3)
Natural Seawater Value: 0.040 mg/L
Acceptable Range: 0.000 to 0.500 mg/L

Potassium (K)
Natural Seawater Value: 390 mg/L
Acceptable Range: 350 to 450 mg/L

Calcium (Ca)
Natural Seawater Value: 400 mg/L
Acceptable Range: 350 to 450 mg/L

Boron (B)
Natural Seawater Value: 4.6 mg/L
Acceptable Range: 3.0 – 6.0 mg/L

Molybdenum (Mo)
Natural Seawater Value: 0.01 mg/L
Acceptable Range: 0.0 to 0.12 mg/L

Strontium (Sr)
Natural Seawater Value: 8.1 mg/L
Acceptable Range: 5.0 to 12.0 mg/L

Magnesium (Mg)
Natural Seawater Value: 1280 mg/L
Acceptable Range: 1100 to 1400 mg/L

Iodine (I¯)
Natural Seawater Value: 0.060 mg/L
Acceptable Range: 0.030 to 0.090 mg/L

Copper (Cu++)
Natural Seawater Value: 0.030 mg/L
Acceptable Range: 0.000 to 0.030 mg/L

Alkalinity (meq/L)
Natural Seawater Value: 2.5 meq/L
Acceptable Range: 2.5 to 5.0 meq/L