Articles Water quality

6 best aquarium cooling methods

June 13, 2016
aquarium cooling methods

During the hot summer months, the temperature in your aquarium can increase quickly. When the thermometer starts to rise, oxygen levels in your tank drop and fish can become overheated. If you’re finding them gasping at the surface it’s definitely time to start cooling your aquarium!

Most aquarists will immediately think of an expensive aquarium chiller, but keep reading for other (and cheaper) ways to safely bring the temperature down.

How not to cool your aquarium

Before getting into the best ways to safely cool an aquarium, be sure to remember that not all “popular” methods are a good idea. Cooling should happen gradually to prevent shocking your fish!

  • Don’t add cold water – The shock of colder water can cause immense stress, which makes fish vulnerable to disease and can even cause immediate death.
  • Don’t add ice bottles or cubes – Like cold water, ice that is suddenly added to an overheating aquarium causes the temperature to decline too rapidly, leading to shocked fish. Once ice starts melting, it may also look tasty to fish and cause little injuries that are prone to infection when they attempt to eat it.
Ice Cube Pile, Day 48, 365/2010, 17/2/2010

Adding ice is never a good idea. Photo by pdbratcher

How to cool your aquarium

During summer, it’s very important to keep a close eye on your aquarium thermometer and start taking precautions before the temperature rises too much. The best ways to cool your aquarium(s) without destabilizing them can be found below. Be sure to also run an air pump, as hot water contains less oxygen.

  • Keep the room cool. It’s a good idea to keep the rest of the room as cool as possible. Closing the curtains during the day and keeping the AC on can really help with this.
  • Turn off the lights. If your plants allow it, keeping your aquarium lights on for only a few hours or keeping them off entirely during the hottest days can definitely help. They produce a lot of heat!
  • aquarium thermometerOpen the aquarium hood. If your stock doesn’t include fish that like to jump, you can allow heat to escape by opening the hood or even taking it off completely.
  • Use the filter. If you have an external filter, cooling your aquarium is a little easier. Running the tubes through colder water or even an ice box can really help, but you have to keep a close eye on everything. The temperature can’t drop too quickly, as this can damage both the fish and your precious cycle. This is a method you may want to skip with smaller aquariums!

Aquarium cooling equipment

If the methods listed above aren’t working well enough for you, it may be time to install some extra equipment.

  • Install some fans. Installing one or multiple small (or large, depending on your aquarium size) fans to blow across the surface of the tank can really help with evaporation and keeping your lights from overheating. You may have some trouble finding them at your local pet-/aquarium store, but clip-on fan systems are available online.
  • Install a chiller. If all the above steps aren’t working for you, you may have to install a chiller. These systems usually aren’t cheap, but if you’ve got a larger tank with precious stock, like a reef tank, show quality fancy goldfish or imported fish, it’s definitely better to be safe than sorry. Like fans, chillers may be a little difficult to find in a normal aquarium store but they are available online.

If you’ve ever had an aquarium overheat, you know how disastrous it can be. I personally know many, many aquarists who have lost precious fish during the summer so I really want to urge everyone to keep a very close eye on that thermometer! Don’t wait too long with taking precautions; keep the temperature stable and safe and be sure to run a bubbler to agitate the surface.


If you have any more questions about cooling your aquarium or if you want to share your own favorite cooling tips, be sure to leave a comment below. Happy fishkeeping!

Cover photo: aquascape by catharticflux


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