A chiller is a piece of aquarium equipment used to keep the fish tank water cool – or, rather, to keep the fish tank from rising above a particular temperature..

What is an Aquarium Chiller?

An aquarium chiller is really a small refrigerator which is installed in-line with an external filtration system to cool – or chill – the water as it passes through the system.

When coupled with a thermostat, the chiller can prevent the aquarium from rising above a per-determined temperature. This can be very important when keeping cold water fish like trout or bass, or when keeping temperate water species like goldfish in a warm climate.

While an aquarium heater will help keep the fish tank warm for tropical fish, a chiller keeps the aquarium cool.


Oranda Gold Fish

Why Would I Want a Chiller on My Aquarium?

If you are keeping fish that need colder water and the higher dissolved oxygen that water provides, then keeping the water cool enough for these fish will be important.

A chiller will help you to maintain the cool water temperature that cold water fish require, thereby allowing you to keep these fish. This becomes more important the warmer your climate – or, more particularly, your home – is.

Sometimes its also required if your tank surface area is not large enough for water evaporation to cool the tank to desired temperature on its own.

What Do I Need to Know About Aquarium Chillers?

Most aquarium keepers, particularly most beginning aquarium keepers, do not have any need for a chiller. Aquarium chillers really are for more advanced aquarium systems.

Chillers are generally designed for larger aquariums. In part, this is because most of the fish that require chillers are larger fish and they need the larger aquarium. Also, cold water fish tend to require more space per fish, so that also mandates a larger aquarium.

Chillers are also usually fairly expensive pieces of equipment – and probably aren’t stocked by your local pet shops, since they are not often needed by the amateur aquarist.