Tips For Keeping Your Aquarium Cool

A typical tropical fish prefers to swim in warm water, something most of us have in common too. Unlike humans, however, tropical fish are a little more sensitive to the temperature they swim in, able only to endure a temperature range of between around 24 and 26°C. Now, here in the UK it is very unlikely for our weather to be warm enough to heat an aquarium to within that range and hence, owners rightly install heaters to keep their fish happy. In the summer months, however, temperatures are occasionally prone to turn up the heat on our aquariums causing its inhabitants all kinds of trouble. Tropical fish are fussy little things you see and as soon as temperatures reach the upper limits of that range, they begin to complain (or would if their little mouths would let them).

The reason for this is fairly simple. Higher water temperatures cause oxygen to escape, meaning there is less in the aquarium for the fish to breathe. This causes the fish a great deal of discomfort and exhaustion, in a similar way to climbers who experience altitude sickness when on the top of high mountains. In serious cases, this oxygen depletion can cause the fish to develop stress related diseases and even die.

Before we explore the ways you can keep your aquarium cool during those rare summer heatwaves, here are two things that you should certainly not do as both can be extremely detrimental to your fishes’ health.

Do not turn the heater off. Heaters are equipped with thermostats that measure the temperature of the water in the aquarium they are heating. When the temperature reaches a certain temperature they automatically switch off, only switching themselves on again once temperatures fall below the ideal range. This helps regulate the water temperature, removing large day-night fluctuations which can be seriously harmful to your fish’s health. Turning the heater off will prevent it from kicking in overnight, when temperatures fall once more. Again, this could be seriously dangerous for your fish.

Secondly, do not be tempted to change out the warm water for cold. This is will not only introduce a serious temperature fluctuation, which will stress the fish, it could also kill of filter bacteria, which are essential for keeping your aquarium clean and your fish healthy. Small water changes can be used to cool the temperature slightly, but avoid taking drastic steps.

So what steps can we take to keep our tropical fish in high spirits?

The most effective method is to install a cooler or chiller into your tank. Aquarium chillers work in a similar but opposing way to heaters, monitoring the temperature of water and cooling it to within the desired range. This is particularly important for large or commercial tanks, where water temperature cannot be consistently regulated with lesser solutions.

Smaller coolers can be purchased from specialist fish stores and some good pet stores. These will fit most domestic tanks and are usually reasonably priced. For larger or commercial tanks, speak to a specialist aquarium dealer who will be able to advise you on a large or custom designed cooling system.

There are other methods that, while cheaper, will not regulate the temperature of your fishes’ tanks quite like an installed automatic cooler. Placing a bucket of ice next to the tank can induce some cooling, as can adding small amounts of cooler water to the tank. Be careful not to add too much or risk causing the fish serious stress. Opening the lid of the aquarium and ensuring it is placed out of direct sunlight can also reduce the temperature somewhat.

To summarise:

  • Tropical fish are happiest in temperatures in the range of 24 – 26°C
  • For most of the year, your aquarium heater will ensure water temperatures do not fall beneath this range
  • Occasionally in the summer months, heatwaves can cause the water temperature to rise higher than the desired temperature range
  • Avoid changing the water or turning the heater off in an attempt to cool water as this can seriously stress the fish
  • Install a cooler to ensure the water temperature remains in the desired range, particularly in larger or commercial tanks
  • Placing the tank out of direct sunlight or near an ice bucket and opening the lid can also induce cooling.