Tank temperature too high. Why?

[FishyFish]

I just got a new 75g tank set up this week and moved my fish over from the smaller tank. I have 2 Eheim heaters in it set to 77 degrees, one of them is on a Finnex temp controller (the other controller is on the way). The tank is consistently reading at 82 though, which is way higher than I'd like it.

What's confusing me is that the 28g tank I replaced was always between 76 and 78. I'm using the same light for now, so why the big temperature difference? The new tank is in the same room and the house temp is 71. I do have two heaters but the one on the controller never turns on because the temp is too high.

I just bought some fans from Amazon to stick on my sump but I don't understand why there's such a big temp difference. Any ideas?

 

[W1ngz]

Hi, me again. I always seem to come across your threads :)
Glass top? That will hold heat. Pumps generate heat. You might have a stuck-on heater. If the temp is always high, unplug the heaters completely for several hours to see what happens. Maybe plug a small desk lamp into the heater controller to give a visual indication of when it's on or off. Don't put the lamp in the tank :P lol

What exactly is reading 82? A thermometer, or the heater controller? It's entirely possible it's reading wrong, see if you can corroborate the temp with some other means.

 

[Justin Cook]

Hi, me again. I always seem to come across your threads :)
Glass top? That will hold heat. Pumps generate heat. You might have a stuck-on heater. If the temp is always high, unplug the heaters completely for several hours to see what happens. Maybe plug a small desk lamp into the heater controller to give a visual indication of when it's on or off. Don't put the lamp in the tank :p lol

What exactly is reading 82? A thermometer, or the heater controller? It's entirely possible it's reading wrong, see if you can corroborate the temp with some other means.

Wow. That's great advice. I'd also be curious to see what the temp is at the heater or wherever else the sensors might be reading from. I usually don't base anything off the thermostats in the heaters themselves but look at thermometers and adjust the "temp" on the heaters accordingly. I keep an analog in the main display and the sump. I've had heaters that were set at 75° and the tank stayed an even 78°.

 

[FishyFish]

Hey again buddy! You're always coming to my rescue! :D

It does have a glass top but the old tank had a covered top too, it was acrylic if that makes a difference. I don't think the heaters are stuck on, the controller hasn't been on at all and I haven't seen the other one turn on at all either, but I will unplug it to be sure.

The controller and a separate thermometer are both reading at 82.

 

[Highgrade]

What is the wattage of the heaters and have they been calibrated? Could your temp probe be faulty? I use a common digital cooking thermometer to test water temp on a regular basis and help with controller probe/heater calibration. As the others stated there are many factors- lights, pumps, heaters, ambient room temp, etc.. that contribute to a tanks temp.

 

[Justin Cook]

Unplug the heaters and see where it stabilizes. Are you noticing the kick on? The lamp idea was great and something I've never thought of. One of my tank just runs a little warmer than the other due to pumps I assume. Fans are a great idea this time of year.

 

[W1ngz]

Bigger tank, bigger skimmer, bigger pumps = bigger heat. Glass retains heat better than acrylic.

Hey again buddy! You're always coming to my rescue! :D

It does have a glass top but the old tank had a covered top too, it was acrylic if that makes a difference. I don't think the heaters are stuck on, the controller hasn't been on at all and I haven't seen the other one turn on at all either, but I will unplug it to be sure.

The controller and a separate thermometer are both reading at 82.

 

[FishyFish]

Thanks everyone! I'm going to unplug the other heater when I get home and see if that makes a difference. The controller I got has a light that comes on so I can tell when it's in use. Hopefully the fans can bring the temp down. I knew bigger equipment made more heat but I didn't expect it to be this much of a difference!

 

[BrandonS]

Where are the probes located. If they are right next to heater it could measure higher than the rest of the system.

 

[FishyFish]

Where are the probes located. If they are right next to heater it could measure higher than the rest of the system.

The heaters are in the sump but the probes are in the DT. They're on opposite sides of the tank so I know the temp is consistent in the entire DT

 

[Taxus812]

Wow does this sound familiar. I even had the same type heater. Thought I was going to come home to fish soup. I even bought a new heater with an external controller etc etc etc.

My lights, pumps and the ambient temperatures in the room (mine was 76F) was the actual culprit. The heater wasn’t even coming on.

$10 clip on fan blowing across the top of the tank did the trick.

EasyAcc USB Clip Desk Fan Mini USB Personal Cooling Fan Portable Table Electronic Fan 720° Rotation for Home Office Dormitory Bedroom etc. - Black https://www.amazon.com/dp/B06XRT1332/ref=cm_sw_r_cp_api_i_Njw7CbRR8D1MF

 

[W1ngz]

My bet then if you've already corroborated the temp reading, is that 82 is simply the balanced temperature difference between the tank and room temperature from the heat of the pumps and the glass insulating it. Fans on the sump might help, but so would replacing at least one side of the glass top with nothing, or a screen top. Fans consume electricity and it's one more electrical thing in close proximity to water. A passive solution might have long term advantages.

Start with the unplugged heater test to see if it's heater troubles or just at equilibrium with room temp. Then start messing with fans and the top.

 

[FishyFish]

$10 clip on fan blowing across the top of the tank did the trick.

EasyAcc USB Clip Desk Fan Mini USB Personal Cooling Fan Portable Table Electronic Fan 720° Rotation for Home Office Dormitory Bedroom etc. - Black https://www.amazon.com/dp/B06XRT1332/ref=cm_sw_r_cp_api_i_Njw7CbRR8D1MF

Thanks! I bought a couple of cheap fans from Amazon earlier this morning and they're being same day shipped. I'll throw them on the tank tonight and hopefully get the temp lowered at least a couple degrees

My bet then if you've already corroborated the temp reading, is that 82 is simply the balanced temperature difference between the tank and room temperature from the heat of the pumps and the glass insulating it. Fans on the sump might help, but so would replacing at least one side of the glass top with nothing, or a screen top. Fans consume electricity and it's one more electrical thing in close proximity to water. A passive solution might have long term advantages.

Start with the unplugged heater test to see if it's heater troubles or just at equilibrium with room temp. Then start messing with fans and the top.

Thanks again! I really want a top on the tank to avoid raising the humidity in the room too much. The aquarium room has several musical instruments in it so humidity is bad. Terrible planning I know, but my house is too small for all of my hobbies! Going topless is not an option because my fish are jumpers but I could try a net top if the fans don't cut it, at least on one side. If I have to go that route I guess I could get a dehumidifier for the room so my instruments aren't ruined.

If unplugging the heaters and adding the fans don't help, I'll remove the glass and try netting. Anything that let's me avoid buying a chiller will be worth it!

 

[Taxus812]

I have the redsea mesh top. Its a PIA to assemble but it is good and sturdy. If you have money to throw at it there are some awesome custom tops you can get as well.

 

[W1ngz]

I really want a top on the tank to avoid raising the humidity in the room too much

Without a chiller, the only way it can cool is by evaporation. Whether this is by an open top, fans or whatever else, the heat has to go someplace. You could lower the room temperature to radiate more of it through the glass, but the primary is always going to be by evap.

A dehumidifier will also help lower the temp by causing more evaporation.

 

[FishyFish]

I got home, turned off the heater which isn't on a controller, and plugged both fans in so they're blowing into my sump. So far the temp has dropped about 1.5 degrees over the last few hours. I'm hoping that it keeps dropping another 3 degrees. Seems unlikely but we shall see.

 

[W1ngz]

Doing both at the same time isn't going to give you the answer if this is a heater problem or not.

 

[FishyFish]

Doing both at the same time isn't going to give you the answer if this is a heater problem or not.

That's a good point. Right now I think I have a thermometer problem more than anything else. The controller has 81, the free thermometer has 79 and the cooking thermometer I tried has 78. Now I'm not sure which to believe.

I'll shut the fans down and see what happens overnight if I just leave the 2nd heater unplugged.

 

[W1ngz]

Maybe you can find someone locally with a high grade reference thermometer. If not, the average of 2 or 3 thermometers will give you a decent value to calibrate the controller to.

 

[FishyFish]

Maybe you can find someone locally with a high grade reference thermometer. If not, the average of 2 or 3 thermometers will give you a decent value to calibrate the controller to.

Thanks, they're all reading between 77.5 and 79 today so I think the problem is solved. Seems like the second heater was causing the issue. I have another controller being delivered today or tomorrow, I'll turn the second heater back on once I can get the controller on it.

I'll keep a close eye on it over the next few days. Thanks again for the help!!