Temp problems.....

I have a problem now that the weather has gotten colder. My tank is downstairs where the temp is lower. Until recently, my MH lights kept the temp at around 76 without a heater. The other day my temp went to 73. So I turned my heaters back on..... Unfortunately I went down the next afternoon and the temp was 81, but the heaters were set at 75 (I have two heaters b/c I heard that was better). The next day I lost two clowns that have been through power outages and 8 degree temp changes. My heaters are in the sump, and my question is does anyone have a problem with their heaters not regulating well and just staying on. One factor for my setup is that water enters the overflow from the bottom of tank, but I am still having a problem understanding why it would heat it up so much. I have moved the heaters to different sections of the sump with no good results. Any advice would be appreciated...

 

Heaters are notorious for failing in the on position. Also a lot of times the thermostats on them go bad, they're pretty cheaply made so it's possible that your dials just are inaccurate. Try figuring out which heater is staying on all the way to 81 and then turn it down a few degrees and see if it happens again. Not a fast way to go about it but it would work.

Also I would recommend looking into a controller, I think you can get the low end ReefKeeper for around $100 and takes most of the guesswork out of it plus gives you some extra benefits.