Cooling your tank in the dead of summer can be a challenge no matter what size tank you have. Drastic temperature changes are detrimental to corals, fish, and other aquatics animals and when your aquarium is small in size, these temperature changes can happen fast. 

When keeping a nano tank, temperature fluctuations are more problematic due to the small volume of water.  Changes just happen much quicker when compared to larger water volumes. This is similar to boiling water, it takes much longer to boil a gallon of water compared to 3 gallons of water.

Ways To Chill Your Tank

When ambient air temperatures rise, so will the water temperature of your aquarium. The most effective way of avoiding water temperature-related problems is simply to maintain a comfortable temperature in your household 24/7. That means climate control inside your home should be set at 68-72° F at all times which is pretty comfortable for most humans. This will ensure the aquarium is not exposed to warm air temperatures that will contribute to rising water temperatures. If you can manage these ambient air temperatures, rising water temperatures should not be a problem as long you use LED lighting and efficient water pumps.  

Cooling Fans

If you do experience rising water temperatures, it usually means ambient air temperatures are rising beyond 75° F. In this case, one of the most economical yet effective options for cooling a nano tank is to use a simple cooling fan. Direct air movement over the surface of your aquarium will have an evaporative cooling effect. By increasing the rate of evaporation you can effectively cool the water.  All you have to do is mount a fan over the top of your tank and angle it so the air blows directly across the surface. 

When using a fan, you will experience a much higher rate of evaporation so you will need to top-off your tank with fresh water more frequently to keep salinity levels stable. Using an ATO system is highly recommended for assuring that the water level and salinity are always stable no matter how much water you evaporate. 


A chiller is the most effective way to chill an aquarium but comes at a cost. While they are very powerful in terms of their ability to drop the water temperatures quickly, they can be expensive to install and operate (electricity) and require some additional plumbing.  

For nano tanks specifically, you have a couple of options. The JBJ Arctica Mini is a small version of a classic aquarium chiller and works the same exact way.  It will require a separate feed pump and dedicated water lines to effectively cool the aquarium water. Water is pumped out of your tank, through the chiller where it is cooled down, and then returns back into your tank.  

The Nova Tec Ice Probe is a unique device that is less cumbersome than a classic chiller but still requires a bit of effort to install.  The probe must come in contact with your aquarium water in order to work so you have to either drill a hole in your tank to install the probe or use a hang-on power filter. The probe will fit nicely through the lid of a classic AquaClear style power filter; install the power filter on the back of your tank and the probe can chill the water as it passes through the filter.  

Helpful Notes

  • Chillers essentially remove the heat from your water and expel that heat into the surrounding air. That means the air temperature around the chiller must be cooler than the desired water temperature in order to work properly. It is not a good idea to place chillers in a close environment where they cannot get steady air circulation to expel the heat.  
  • LED lighting transfers little to no heat into your aquarium and has dramatically reduced the risk of rising water temperatures for most hobbyists. If lighting is the source of your heat, consider LEDs instead. 
  • Maintaining a comfortable air temperature inside your home should suffice for keeping your tank within an acceptable range. If not, find out what is causing the rising water temperatures; usually, pumps and lighting are the #1 source of heat. Upgrading to DC pumps and LED lighting is usually more than enough to eliminate heat problems.
  • In the case of an emergency (A/C unit is on the fritz), you can freeze sealed bottles of water and float the frozen bottles in the aquarium to help keep temperatures down. Replace the bottles daily until you can control air temperatures again.