How to cool your aquarium in summer

Written By Adam Farrelly


During prolonged periods of warm weather, your aquarium may well overheat, reaching temperatures that are detrimental to the survival of your livestock.

marine salt water yellow tang

Different species will react differently to the heat, some may not react at all, others will gasp at the surface;

and in saltwater aquariums, corals may bleach. It is important then to attempt to get the tank's temperature down, and if this is not possible, put measures in place so that it can handle the heat.

In this brief guide I shall discuss the effects of warm weather on aquarium livestock, how to cool a tank down as well as solutions for dealing with the consequences of elevated temperatures.

Too Hot To Breathe

When an aquarium or pond gets warmer, the dissolved oxygen levels in the water decrease. This usually leaves fish lethargic or gasping at the surface. For saltwater aquariums the same is true, although the high flow environment of a marine system compensates for the oxygen loss somewhat. The main effect on marine systems will be stress on the corals, SPS (Small Polyped Stony) corals in particular do not tolerate temperature swings well, and may bleach or strip.

Time To Cool Off

To reduce the temperature of the tank as well as make the fish more comfortable, there are thankfully a number of solutions. The first and simplest solution is to improve the ventilation of the tank space. Unless your fish jump, remove the tank lid, then open windows and use a desk fan if one is available. If the tank is getting direct sunlight, close any curtains or blinds. Alternatively, freeze a bottle of water and float this on the top of the tank to reduce the temperature; consider having another on standby to rotate frozen and thawed bottles.

For saltwater aquariums, a chiller such as the DD DC750 Refrigerated Chiller is also an option. This will works seamlessly with the DD temperature controller and DD Titanium Heaters; and is a great all round temperature control solution.


DD DC750 Chiller


As an addendum, never pour cold water into your tank directly to attempt to reduce temperature, as this can cause shock to the livestock and may result in deaths.


All aquariums and ponds should have adequate aeration, but if not, there are a wide variety of air pump options available which will keep fish comfortable and keep oxygen levels from dropping excessively. In tropical aquariums, temperatures of up to 30 oC are tolerated by most species with adequate aeration. In marine systems, good flow combined with an open top setup is sufficient for most systems, and helps reduce temperature through increased evaporative cooling.




There are a number of air pumps available here at The Tetra APS range for tropical and saltwater aquariums is a wonderful air pump, which stays silent thanks to a sound absorbing bellow housing and comes with a 3 year guarantee.


We at are always available to answer any questions you may have. Feel free to contact us on the links below or drop us a message on the website.

AquariumCooling your aquariumMy fish tank is too hotTemperature

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