An aquarium heater is a device used to warm up the water of your fish tank. To keep fish healthy and happy, it’s important to maintain a stable water temperature and to reduce temperature fluctuations. The aquarium water heater has a thermostat inside; it constantly monitors the water and will switch off once the desired temperature is reached.
Whether or not you need an aquarium heater depends on what type of fish you keep. If you have tropical or marine fish, then the water in your fish tank needs to be warmer than if you keep coldwater fish like goldfish or bettas. Even so, it’s recommended to have a heater running during cooler months to keep coldwater fish active and happy.
As a general rule, we recommend 1 watt per 1 litre of water. To run the most efficient aquarium heater, it is better to round up to the larger size when calculating which heater to buy. This is because a larger heater will heat up the water faster and stay switched off for longer. A heater that is too small, or not powerful enough for your tank, may cost more to operate in the long run.
Please also check the manufacturer’s recommendations when choosing a heater. For example, Aqua One recommends their 300 watt aquarium heater for a 300L tank.
However, as their heaters are larger and more efficient, Eheim recommends their 300 watt aquarium heater for tanks between 600L–1000L.
Submersible fish tank heaters are best placed near the output of the filter so heat can be evenly dispersed throughout the tank. Position an aquarium thermometer on the opposite end of the tank so you can monitor the temperature of the aquarium.
Place aquarium heaters at a 45-degree angle to prevent them from switching off prematurely. If a heater is set in an upright position, the thermostat, located at the top of the heater, could be accidentally triggered by the ambient heat rising directly from the heating element.
It usually takes around half an hour for an aquarium heater to heat up the water in a fish tank. This will depend on the current temperature of the water, how strong the aquarium water heater is, and the size of your tank. It may take up to a couple of hours to heat up larger tanks.
Shop online at Aquarium Kingdom and browse through our range of the best aquarium heaters for your fish tank. We have a large selection of submersible aquarium glass heaters, external inline heaters, and nano heaters to keep your aquarium at the right temperature for your fish.