Aqueon heater too warm for my tank

[Chickadee26 46]

I dug out an old Aqueon 100 watt heater to use in my 10 gallon tank. No matter where I set the temperature, the temp in the tank hovers around 80-81 F, which is a bit too warm for my neo shrimp. I keep lowering the dial a degree, but the temp won't budge. I went as low as 72 F and the tank temp is still 80-81 F. I know it's not the thermometer because I put two in the tank (regular and digital) and they are consistent.

I then decided to try an old Top Fin 25 watt heater that I used for my 5g tank. The temp is now 78.8 and stable. I'd like to get it a degree or two lower, but will do it gradually.

So what do you think the problem is with the Aqueon heater? Was the wattage too high for this small of a tank? Or could the thermostat be malfunctioning? Is this a common problem?

 

[Essjay45 160]

It is known issue with heaters of any brand that they can fail by sticking in the on position and can end up cooking the fish/shrimps.

The way to test it would be to turn the suspect heater to its lowest setting and put it in a bucket of water. If it heats that to 80 F, you'll know it's faulty.

 

[Rusty_Shackleford45 160]

I dug out an old Aqueon 100 watt heater to use in my 10 gallon tank. No matter where I set the temperature, the temp in the tank hovers around 80-81 F, which is a bit too warm for my neo shrimp. I keep lowering the dial a degree, but the temp won't budge. I went as low as 72 F and the tank temp is still 80-81 F. I know it's not the thermometer because I put two in the tank (regular and digital) and they are consistent.

I then decided to try an old Top Fin 25 watt heater that I used for my 5g tank. The temp is now 78.8 and stable. I'd like to get it a degree or two lower, but will do it gradually.

So what do you think the problem is with the Aqueon heater? Was the wattage too high for this small of a tank? Or could the thermostat be malfunctioning? Is this a common problem?

My thoughts:
1. All heaters WILL fail at some point. It might be in 6 months, it might be in 10 years, but it will fail. Unfortunately they always seem to fail in the on/heating mode.

2. I always tend to undersize my heaters for a couple of reasons. It's preferable to have your heater come on and stay on longer rather than coming on heating up the water quickly and going through multiple on/off cycles. The on/off cycle is usually what contributes to their failure. I also don't want to heat the water too quickly for the fish. I currently have a 150 watt heater on my 36 gallon tank. On average it takes about 2 hours of heater time to raise the temperature 2 degrees. Longer run time, less on/off cycles. 100 watts on a 10 gallon may be too much? 50 watts may be better, but see #3 first.

3. At this point you have 2 choices. Go and buy another heater and wait for it to fail. Or go buy an Inkbird temperature controller which will allow you to use your current heater (or any heater) without worry that it ever will get too cold or too hot. You can set your preferred temperature as well as what point you want the heater to turn on. Big and accurate LCD display. Alarms if your water gets too warm or too cool. About the price of a new heater.

 

[Chickadee26 46]

Thanks both for the helpful replies! I am testing the heater in a bucket of water now. So far the 25W replacement heater is doing the job, but I will look into a more reliable option.

 

[GaryE6 4]

Your story is one I've met up with many times. I really mistrust heaters, and may look into the inkbird controlers.

 

[Rusty_Shackleford45 160]

The Inkbird models with wifi also allow you to keep a graph of tank temperature.

 

[Jennet25 83]

I remember seeing on a Youtube video someone saying about having two smaller heaters in an aquarium being better than one large one due to this problem. That way, less likely to cook fish when one goes. I thought about this at time and did not action it. May well do that now, as it makes a lot of sense. Anyone any idea what wattage I can get that will work in an 80 litre / 21 gallon aquarium measuring 60cm long, 30cm wide, 45cm deep.

Inkbird temp monitor no good to me as I don't take my phone upstairs to bedroom with me, and live in an old house with thick walls. Would need a siren to alert me. Also, can't seem to get brain to work today.
Thanks