Answer by
StingRay (471)
The depth is not so important as the wattage per gallon. If you have just fish and live rock, 1/2 watt per gallon is fine. 1 watt per gallon is required if you have clams, anenomies, fans, and the like. So if you have a 100 gallon tank, you'll need either 50 or 100 watts of power.