Heater or no heater?

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Oct 29, 2020
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I’ve been working my tail off trying to finish off jobs before the holidays for the last few weeks.

It’s getting down to crunch time, and kids are in bed, presents are wrapped and ready to go under the tree.

So I have a bit of time before I hit the sack for the night. I popped onto YouTube and video about whether or not heaters are necessary for the average home aquarium.

I have been thinking about this for a couple weeks now, as my tank stand is situated over a heat run in my son’s room, and I have several holes drilled to allow air flow to provide heat to his room.

i have not checked the ambient temperature of the room on a day to day, or hour to hour basis.

I have been able to bring down the temperature of the inside of the stand by providing adequate air flow.

My central heating is set to 65F at night, and 72 during the day.

the thermostat is located one floor lower than the aquarium, so as heat rises, it’s going to be warmer upstairs that it is downstairs.

everyone once in a while I catch my aquarium heater turning on when the water is already warmer than my target.

I can for certain say that the thermostat on the aquarium heater is not calibrated properly, because I have the dial set to 63F and it still turns on to heat at 7.

I want to maintain between 74-76F temperature, and I think I might be hesitant doing so going into the colder months.

I have a Eheim 100w heater which is way overkill for the tank setup here, but I just imagined the on-off cycles would be less, possibly extending the life of the heater. Now that I type it out onto a forum, I’m not sure that logic works out.

i have not tested anything yet, but I think my home heating can support the temperature range I’m looking for.

I am keeping right now:
Cory pandas
Neon tetras
Nerite snails
Amano shrimp

I’m not sure I need the heater in the tank, especially when it’s running out of calibration. Between the heat from the house, and running equipment, I think the temperature will run somewhere in the middle for everyone’s enjoyment.

that being said, in case the furnace goes down I have a way to heat the tank, but I don’t want to wear and tear a heater if I don’t need to.

Anyone else have thoughts on this?


Fish Guru
Jan 26, 2008
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Perth, WA
I had heaters in my tanks during winter but not in summer because the air temperature was sufficient to heat everything.

In winter I had my heaters set on 18C and they sat on that.

In a well insulated house, the electrical appliances and internal heating is usually sufficient to maintain the water temperature at a suitable level for most fish. However, it can vary depending on how hot/ cold you have the house temp. But for the most part, you could probably turn the heater off and have it for emergencies or as a back up. Alternatively, set it on a lower temperature (22C) and see how the tank's water temperature goes. If the water temp stays stable because of the house temp, that's fine. Turn the heater off and put it away somewhere safe.

The only thing you will need to worry about is doing water changes with cold water. If you add cold water to a tank without a heater, it could take 24 hours or so to warm up to room temperature. This could stress or kill fish if there is a major difference in temperature for a long time. You could overcome this by adding some boiled water to a container of tap water to increase the temperature of the cold water and bring it into line with the tank's temperature.

Or use warm water but that depends on if you have a storage hot water system or instant hot water system. The hot water storage systems can leach copper into the water and this can kill snails and shrimp in the tank. Instant hot water (like instant gas systems) don't leach copper into the water because they use cold water and heat it as the cold water passes through the heating elements.

You can also insulate the base, back, sides and top of the tank to help hold the heat in overnight. Polystyrene foam sheets can be stuck on the outside of the tank (back, sides and base), and coverglass can go on the top.


Fish Aficionado
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Mar 22, 2020
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If tank temps dip under 72, def a heater as otos will need the temps higher.

If it stays in the range you want, good to go :)


Fish Gatherer
May 13, 2011
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Central New York, USA
First, the 'set point' rheostat knob of most heaters is nearly never spot on, more like a guide and a thermometer gets you to more accurate actual temperature. Check out: Aquarium Heater - Is One Really Needed?
Bottom line, I tend to think that it's better to have one even if it only cycles occasionally, then not to have one and have some species stress ... or worse.

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