[Myka]

My 90 hasn't had a heater on it in quite awhile, but I usually use two smaller heaters rather than one large one because when heaters fail they usually get stuck in the on setting and cook the tank. If two smaller heaters are used, one stuck on will not be enough to overheat the tank. My tank does best if it is not over 80 degrees. I try to keep it around 78, but it is almost always 79-83. The halides heat the water enough during the day, and there is enough water volume that it doesn't drop much at night. Just a couple degrees of variance daily. Right now it is 79 degrees when the lights first come on, and 81 when the lights go off.

It depends how warm your room is too. If the room is only 60 degrees and the tank is 80 degrees it will take a lot more heater power than if the room was 70 degrees. Put a thermometer in your room near your tank, and you may be surprised how much lower it is than what your furnace says.

I have one system that is about 60 gallons, but has a lot of plumbing on it and is in a cold room (~60 degrees), and it takes 350 watts of heaters to keep the tank at 79 degrees.