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Is a heater required?

C

CDNDavid

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18 Mar 2025
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Hello,

I have been reading/watching some info on if heaters are actually needed. For example Cory's video from aquarium co op.

For info, I have no plan to breed and tank is a 90L. Room temp is between 22-23c. For fish I am thinking a school of Head & Tail Light tetras, some Corydora's, and 1 Apistogramma, plus a couple Amanos.

I think the Apistogramma is the one that could be a problem? I have been looking at either Cacatuoide, Macmasteri or Calamar.

Thoughts on going without heater?
 
In my experience. tank temperatures (without a heater) are a few degrees below room temperature. In your case, that would make the water. 20-21C.

Cory has climate control (the same for MD), so maintaining the temperature is constant all year round. If you cannot maintain the outside temperature, then that would mean the aquarium is at the mercy of nature.
 
For most fish (and this is really a very general statement) 22-23 is their comfortable lower limit, unless you specifically pick ones that are comfortable below that of course.

I would do a test with your room and see where the temp sits in the aquarium/test vessel for a few days. And then select fish within that range if you want to go no heater.

Cory and MD do do this successfully, so it is viable. I could not do this as I don't have climate contol and most of the months in the UK would see the fish very cold indeed!
 
hypnogogia said:
That seems to be against the laws of physics…
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Probably a very unscientific observation on my part!

During the summer, my kitchen was at 29 degrees, with the aquarium water at just under 28. If the law of physics says I am wrong, then I'll bow down to that science rather than my mickey mouse science observation.
 
hypnogogia said:
That seems to be against the laws of physics…
Click to expand...
Although I would say that I thought evaporation could account for my differences. I really think that the outside temperature and water temperature are not always in sync. Anyhow, I think my overall point is that heaters do provide you some stability (and backup), so just relaying that to the OP. I would hate to say that your tanks would be exactly the same as the room temperature constantly and then have environmental problems.
 
Bradders said:
Although I would say that I thought evaporation could account for my differences. ...
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Evaporation lowers the temperature significantly. Without a lid, the aquarium without a heater will in most cases have a lower temperature than room temperature.
I have a lid on all my aquariums and the temperature is about 1 to 2 degrees Celsius higher than the room temperature. Pump and lighting increase the temperature in my case. When the room temperature is high, I raise the lid a little so that the temperature drops or at least doesn't rise too much due to more evaporation.
 
I find barbs, tetras, rasbora etc. behave more sluggishly and stay at the bottom of the tank when temperatures are 20-22C - when I forget to plug the heater back in after a water change. They seem more energetic and engaged at 25C. I heat the caridina/neocaridina shrimp tank to 22C now vs. passive at room temperature. I don't know if that makes a difference but suspect that it does. I don't go higher than that otherwise there is too much evaporation.
 
If the room temperature is a consistent 22 - 23° I can't see a problem of with keeping some of the more temperate fish. The only fish that I have always wanted to keep, but never have because my tanks have been too warm, Corydoras (or whatever they are called nowadays) Barbatus.
 
CDNDavid said:
aesthetic reasons and 1 less piece of equipment.
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There are integrated heater canister filters from Oase/Eheim etc in case you aren’t aware. (You probablly are and it only addresses your initial point). If the room is temp controlled at around 22-23 then you should have a huge selection of fish to choose from.
 
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