Our tank is a 40 gallon, and we have a 125 watt, clear and aten?, supposedly twice what we need, they were doing really well until we moved two months ago, now they just don't happy :-( They are positioned about midway and higher in the tank and I have two power heads going, I added Iodine tonight, not sure if it was low that is something we have never checked. PH, nitrates, nitrites, amonia and calcium is all good, salt is at the ideal level, temp. is 80.8 with the light off, I'm sure it gets warmer when the light is on