Tank Temp Confusion

[BioCube14]

I have noticed my heater and my thermometer dont seem to be accurate. I keep my ambient room temp about 75. My heater set to 78 Hydor theo heater and my thermometer says 82. When i turn off my heater the temp in my tank go to 79-80 tops when the lights are on. The thing is I need my heater on because if i dont have it on my temps when my lights are off slowly drop to about 75 degrees. I guess what im saying is I need to figure out a way to stabalize my temps. I have a biocube. Im guessing i should just keep the heater off during the day and put it on a timer to only work when the lights are off (at night)? Is my heater screwed up? i set the heater to 78 and tank is showing it is 82 and the red light on the heater says it is on shouldnt it turn off when temps are above 78?? Anyone have this problem?

[merlin0883]

with a tank that size, it can be difficult to get heaters to work properly. I usually use larger heaters than i need, and they just don't have to work as hard--but i use like a 150gal heater on a 55gal tank. if you use too large of a heater on a very small tank--like under 20gal--then it takes no time to raise the temp too high. make sure your heater is of recommended size. also, the thermostats in the heaters are horrible. i have found that submersible heaters are better, but still allow about a 3 degree fluctuation between the set temp. if the ambient temp around the aquarium changes, it will also disturb heater function. if you use metal halides on that small tank, then you may have already identified the problem. i would recommend putting the heater on a timer opposite ur light, but this can also present another problem--if you plug a heater in and take time to get it right, which can take 3-4 days to do, and unplug it/cut the power, it doesn't always keep the same adjustments when you give the power back to it. if its power is cut and regained every day by a timer, it may fluctuate even more than it does now. try it, but keep an eye on it. if u have no luck, get a new heater, and don't go cheap. get a new thermometer. good luck.

[Bill S]

The risk associated with using a large heater is that they can and will occasionally get stuck on. I'd rather use 2 smaller ones than 1 big one. As well, the dial on the heaters isn't particularly accurate many times - just like the thermometers aren't.

In your case, I'd try a new heater...

[BioCube14]

yea i think i might do that I thought hydor theo was the best out there but i guess not maybe i'll try ebo?

[LoneStar]

Go with the Ebo-Jager

[caferacermike]

Ebo Jager, best without getting way to complicated. Personally I prefer not to even bother with heaters. I'd rather have a gentle 5 degree swing day to night than to ever cook my fish.