Aquarium Heater

Based on their temperature preference, fish can be grouped into two general categories: temperate and tropical. Temperate fish include many species that inhabit cooler waters. However, the fish most commonly seen in freshwater aquariums belong to tropical species. The term “tropical” refers to natural habitats where the waters are warm throughout the year. It should come as no surprise, then, that it is necessary to maintain your aquarium within a specific temperature range. This is the job of the aquarium heater.

This essential piece of equipment maintains your tank at a constant temperature, regardless of the room temperature. With the exception of a few fish, such as the common Goldfish, the species you are likely to keep as a beginner will require the aquarium temperature to be maintained at 75 to 79 degrees Fahrenheit (24 to 26 degrees Celsius). However, this is entirely dependent on the species, and you should consult your local aquarium dealer or one of the many fish encyclopedias for specific temperature requirements. Obviously, you should not mix species that have very different temperature requirements.

There are a few types of aquarium heaters available to the aquarist, but the most common is the submersible glass tubular heater with a built-in thermostat. This heater attaches to the side of the tank and has external controls. Once it is properly set, it automatically responds to changes in water temperature and turns itself on and off. If you choose one of these, I recommend that you double-check the accuracy of the dial with a thermometer.

In general, you should place your heater close to an area of high circulation so that heated water can be rapidly and evenly distributed throughout the tank. This is usually near the filter system or the airstones.

Heater size largely depends on the size of the aquarium. The general rule is 5 watts of power for every gallon of water. Thus, a 20-gallon tank requires a 100-watt heater. Many fishkeepers recommend that two heaters be used in aquariums over 50 gallons; this allows for more even distribution of heat in the aquarium and also maintains correct temperature if one heater fails. The total required wattage should be divided between the two heaters (so a 50-gallon tank would require two 125-watt heaters, for a total of 250 watts).