How to cool down fish tank in the summer?

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Aquarium Advice FINatic
Jul 17, 2010
How to cool down fish tank in the summer? I also have a 40 gallon fish tank in my bedroom. Right now is at 80 deg. But what happens in the summer? I have one tank in my living room, and I have ac to bring down the heat in the fish tank. I also have a 40 gallon tank in my bed room with no ac. I forgot all about that. Can I use frozen water in a bottle to cool down the tank? I can not use a fan, because of my cat, that is why I have lids for all my fish tanks. I can un plug all the heaters as well.
Is aquarium temperature really that much of an issue for you? I live in the UK and we don't have hot summers or AC, but my aquariums that are typically 24/25c (75/77f) can get upto 30c (86f) for a week or two in the summer without any problems. This has happened the last 2 summers when we had record breaking temperatures.

Most heaters work with a thermostat, so they automatically go off when the water reaches their set temperature. So turning off a heater wont make any difference if its thermostatically controlled.

Lights will heat up an aquarium a little, so turning off the lights will lower aquarium temperature more than turning off the heater.

Removing the lid and running a fan over the surface will promote evaporation and reduce aquarium temperature. But you don't want to do this because of your cat. We have a cat too.

There are aquarium chillers, but they are expensive. Thats really the only way to get an aquarium temperature below whatever your room temperature is at. So controlling room temperature is the better way to go. Close curtains and windows during the day, open windows at night to promote nighttime cooling. Turn off any appliances that don't need to be on. Maybe consider getting a small evaporative cooler for your bedroom.

The biggest problem with warmer water is that it holds less oxygen than cooler water. So make sure your water is well aerated to maximise oxygen content if the temperature gets higher than normal.

I wouldnt try using bottled frozen water to control water. Ive heard some people do this, but all you are going to do is create temperature swings that are going to be more hazardous than just letting the water naturally settle to the room temperature when its warm.
Guppies can handle the warmer water as long as there is enough oxygen in the water. If need be, get a spare air pump so that you can add an extra air stone or bubbler for when/if the temp gets above 85-86.

As Aiken mentioned, using frozen bottles is more likely to cause problems than cure them. Just keep the room dark during the day and that will help keep the temp down some. Even better would be to close the door so the cat can't get in and open the lid and use a fan during the heat of the day.
Thanks to both of you, for all your help. I would close my bedroom door but my cat would just run out the door. I could move my litter box, but my bedroom is connected to my sleeping room. I tried before and I have to go chasing after my cat, She loves my bedroom and she likes to run in the hall way. She is very sneaky. lol ..I will have to get a air stone for the tank.
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