How to Cool Your Tank When Summer is Heating Up

How to Cool Your Tank When Summer is Heating Up

lower temperature aquarium thermometerThis article will identify the effects of heat on an aquarium and offer some simple techniques to lower your temperature.

Summer is back once again, with it comes the heat and algae!  Without the proper tank set-up or preparation, high temperatures can quickly become the worst nightmare of any aquarist.  Imbalances will not only affect fish, they can also be detrimental to aquatic plant and coral growth.

Algae control can get out of hand quickly if the tank is left in the sun by a window, near bright lighting, or faulty tank equipment. This guide will help you find the best, quickest, and cheapest methods to reduce your tank’s temperature this summer.

Our community has also gathered other tips for starting an aquarium, hopefully they are helpful in your setup.

The process in which heat affects the ecosystem is simple: fish metabolisms rise with the temperature, creating a need for higher levels of oxygen in the water. Meanwhile dissolved oxygen levels drop as temperatures rise, compounding the problem. 

In addition to the strain put on fish health, coral and aquatic plants will suffer, as they also rely on plentiful amounts of dissolved oxygen in the water.

reduce tank temperature How to keep your tank cool and suitable for fish & plants this summer

Any tanks with fish must be kept below a maximum of 86° to ensure their safety. For all species of fish, there is a middle ground in which they are happiest, and they must be kept within that range for optimum health. Examples: Tropical fish – 72° – 80° F (optimal is 78º), Common Goldfish – 65º – 68º F, Fancy Tail Goldfish – 65° – 72° F.

There are a number of methods for keeping your tank cool, but the correct answer will be determined by the aquarists’ circumstances and fish inhabiting the aquarium. We would like to know the tips you use to keep the temperature suitable for all members of your aquarium, please leave a comment below.

These will be your best methods to reduce the heat:

  • Air conditioning: Yep! This is one of the most essential elements to keeping an aquarium at appropriate temperatures.  A cool exterior environment will, in most cases, prevent aquarium temperatures from rising out of safe range.
  • Get a tank chiller: In the event that air conditioning isn’t enough, you may have to purchase (price range from $100 to thousands depending on size) a tank chiller.  This costly yet surefire method is very effective at controlling temperature and can be used alongside a heater for maximum climate control.
  • Install a good filtration system:  Aeration is key in making sure water isn’t exposed to higher surface temperatures for too long.  In addition, you get the bonus of filtering at the same time: win-win!

Affordable, free, and/or quick fixes to lower the temperature:

  • Frozen water bottles:  Thats right.  Freeze bottles of water for temporary aquarium ice cubes.  It won’t break the bank, and many aquarists even swear by this method’s effectiveness.
  • Run a fan directly on the surface: This is a quick and easy way to make sure that the same water doesn’t remain at the tank’s surface for too long. Be aware this will increase the evaporation rate of the tank.
  • Reduce natural and artificial light: Even if it’s only for the hotter months, install blinds in your aquarium room to block out light when temperatures rise.  Also, cease or reduce use of artificial aquarium lighting.  Remember, your aquarium won’t be shimmeringly beautiful for long if it gets too warm!

Have you used a different solution to lower the temperature in your aquarium?

Let us know your method in the comments area below the post.

Not everybody wants or can afford an expensive chiller, so for all of our benefit please spend a few minutes to explain your technique. We wish to ensure the success of every hobbyist and if you have any other questions, please ask the experts in our aquarium forum.


  1. Ive been using frozen bottles of water this summer (14 of them as i have an 8ft tank) but will have to buy myself a deep freezer for next year as i have no room left for my own food with all the water bottles in my fridge freezer…this has helped drop the water temp from an alarming 30% c to 25%c. I also have a very good air supply but i am an amatuer still and am Always looking for new ideas…

    • Wow! That is some dedication!

      I have a small 300 litre fridge and might be away for these summers with someone feeding them twice and cleaning the aquarium fortnightly.
      However, my house gets HOT. Hot to 45*C+. And, I do not have airconditioning.
      If I leave the fish alone in this house, they shall be roasted!


  2. That’s dedication when you give up the space in your freezer for your fish. I usually just
    take the heaters out of my aquariums in late May, when in the Northeastern part of the United States the temperature warms up considerably.

    There’s more fluctuation in temperature, however, overall the water in the tanks does drop
    by a few degrees. Most important the fish seem happier.

  3. I have a betta fish in a house with air conditioning. Temp set at 72. I have a preset heater in tank usually runs 79. This summer huge amt of algae. New tank with strong light. Bought a dimmer switch but algae keeps coming back. In a shady window with a decor backing on tank. Its a Pisces 5 bullet shaped tank. Thanks.

  4. I live in a cold area and not much of high heat problem during the summer too. The aquarium is set far from the window so no direct sunlight and the room is pretty dark.

    So room temperature is around 22-24° C. And I am struggling to maintain temperature on my 4ft tank. Water sometimes reach 30°C. Which causes low oxygen level. Running air pumps also internal filter to get some surface agitation. I am running the heater at 24°C currently but my tank easily goes to 28°C. Any advice on how to maintain this around 26°C.


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ATTENTION SHOPPERS, Prices on all sizes of Nualgi increased on January 1, 2021.