A constant, appropriate water temperature is vital to keeping your aquarium inhabitants healthy. A sudden temperature change can place undue stress on your aquatic life, increasing their susceptibility to infection and disease.

Aquarium setups, reef aquariums in particular, often employ equipment (lighting and water pumps especially) that produce enough heat to raise water temperature. Without a chiller to decrease water temperature, aquarium water can warm to a point where it no longer holds enough oxygen to sustain the inhabitants.

If you need a chiller, plan to install it into your system as early as possible. Chillers are external units that often require plumbing and always require adequate space and sufficient ventilation. They give off significant amounts of heat when in use - in fact, you should avoid placing your chiller in an enclosed aquarium stand, because it can give off enough heat to raise water temperature. It may also cause the chiller to overheat and not work as effectively.