Heater Problems

[bluespotjawfish]

I have a 125 gallon tank. I have been using two heaters, one in the sump (100w), the other in the tank (200w). My tank was stable until I had to replace the tank heater. After I replaced it, my temps were all over the place (even when set very low), like it was sticking. So, I replaced that one with yet another one (a 150 watt). Each of these have been a different brand (Aqua, Stealth, Hydor, and now Ehnem).

The house temp is typically at 72 degrees, which generally means the tank ranges from 78 to 79 degrees (without and with lights). To keep the temp right I run fans to keep the tank cool with the MHs. Last night after the lights were out for several hours the tank temp was 81 (the heater is set at 76), I unplugged the new heater and this morning it is 76 with just the one heater running.

So, one heater doesn't seem to be quite enough (especially if fans are left on at night and the house temp drops). Two seems to be too much.

Any suggestions?

[tbittner]

I thought the heaters were thermostat controlled, therefore the ability to set the desired tempature. I wouldn't be suprised if your second heater is also bad.

[Dentoid]

Why don't you plug your heaters into your ReefKeeper and let it turn them on and off. I wouldn't let the heaters thermostats control the temperature. Also you have two thermostats at different places in the tank. Theoretically, the overall water temperature should equalize throughout the system. But the sump water could be staying cool enough to keep that heater going, especially if a fan is running over the sump water. By using the ReefKeeper and its temperature probe you are taking a temperature reading form one place, not two (as in two heaters=two thermostats).

[mps9506]

I agree with Scott here. I am a big advocate of using an external controller for thermometers.
As far as your fans getting left on at night, can you plug them onto the same outlet with the MH's? That way they only cut on with the halides and cut off when they shut down?