Boil your fish

[Eric]

Well, it almost happened. We woke up one morning and the 35 gallon tank was hot. Not just warm, HOT. Off the temperature scale. The heater (a THEO submersible) was set for 76 degrees. I immediately turned it down as low as it would go, but it staid on. So I took it out and am using a different brand heater now. All the fish somehow survived (Guppies, Platys, Tetras, swordtails, and a snail).

My 120 gallon has a submersible 400W THEO heater in it. I'm finding it a little difficult to maintain a constant temperature. The heater is mounted horizontally down low (for maximum efficiency) in an area where there's plenty of water flow. I set it and wait for the temperature to get to where I want (about 76 F), then I turn the dial so it just goes off. That should do it, right? But often the temperature will exceed 80 F and the heater is still on putting out heat. Other times the temperature falls below 76 and the heater doesn't come on. I have plenty of water action - I don't believe I have any dead spots (certainly not where I placed the heater). and I have thermometers at both ends of the aquarium.

Anyways, I'm just wondering what options are out there to more accurately maintain a reasonably consistent water termperature.

[BillD]

Sounds like the thermostat in the heater is not functioning properly. This could be a product of the brand. Some are more accurate in maintaing temps than others. I also believe that to avoid boiling, use a smaller heater, or on a larger tank, 2 of them. So, in the case of the larger tank, 2 x 200 watt heaters instead of one 400W. For a 35, you shouldn't need a heater of more than 100 to 150W, unless the room is really cool. If the fluctuation is minor I wouldn't worry about it. From what I have read on multiple forums, people very much like Visitherm Stealth heaters, or the old Ebo Jaegers. People are less enamored of the new Eheim Ebos. Regarless, I think more fish have been boiled by faulty heaters than have frozen, so go small to prevent it. I don't heat any of my livebearer tanks, and they are all in the basement. I also think that a heater that is oversized will cycle more often than a properly sized one, thus shortening it's useful life.

[zenins]

All good advice, I agree with it all :)

I find that the Tronic heaters keep their temp pretty well,
no mechanical points to stick or malfunction, it has an electronic circuit.
I use the Stealth heaters as well :wink:

[Eric]

Wow BillD; I wasn't expecting all that !! That is great information and some really great ideas. I'd really hate to wake up one morning to 120 gallons of Cichlid soup. I was told at the fish shop that my tank requires a 400W heater, and they only had the THEO brand with that wattage. But two 200W heaters is an excellent idea for the reasons you specified. So Stealth or Tronic (thanks zenins too) are strong contenders.

[Eric]

Last night the aquarium temperature was 76 degrees and the heater was not on. This morning it was just under 87 degrees. So I just replaced the 400W THEO heatert with two Stealth 200W heaters. I like them! As I write this, the temperature is 81 degrees and slowly falling.

I know the tempertures my tank has been experiencing is within tolerable range for my inhabitants, but those wild fluctuations can't be healthy for them. Hopefully my new heaters will help correct that. I really appreciate the advice.