How to install a submersible aquarium heater

Updated November 21, 2016

The temperature of your aquarium is essential to the comfort and health of your fish and plants. Like other cold-blooded creatures, fish rely on stable water temperatures to survive and maintain health. To accomplish this, install a heater in your aquarium. Of the different types of aquarium heaters available, submersible aquarium heaters are the easiest and safest to install.

Remove the submersible aquarium heater and the suction cups from the package.

Remove the twist ties from the cord.

Examine the aquarium heater for breaks in the glass or plastic housing.

Clip the suction cups approximately one to two inches from each end of the submersible heater.

Set the temperature switch. There should be an arrow or band of colour denoting the ideal temperature for an aquarium. Set the gauge to within this mark.

Place the aquarium heater in a pot of water deep enough for it to be submerged and plug it in.

Check the aquarium heater in three to four hours to ensure it is heating properly. Insert a thermometer and check the water's temperature. It should be between 20.6 and 26.7 degrees Celsius.

Install the heater in the centre of the back of the aquarium, at least three inches from vegetation, fake plants and other aquarium devices. Press the suction cups firmly to the wall of the aquarium.

Plug the heater into a surge protector or wall outlet; establish a "drip line" with the aquarium heater cord.


The submersible aquarium heater can be installed vertically, with the end with the switch on it at or just below water level, or horizontally, with the suction cups attached to the bottom of the tank under the gravel or on the back side of the tank just above the gravel. Since heat rises, the lower the aquarium heater is installed in the aquarium, the more efficient it will be. Different types of fish and aquaculture prefer different temperatures of water. Research your fish's preferences in temperature and adjust the aquarium heater accordingly before installing it. An incorrect water temperature can result in fish loss, diseases, over breeding, algae blooms, reluctant plant growth and fish refusing to eat. Install a separate aquarium thermometer in the aquarium and monitor the temperature daily. Submersible aquarium heaters need to be replaced every six months to a year. It is a good idea to have a spare aquarium heater in case the heater quits working or becomes damaged.


To avoid electrocution, make sure the heater is void of any defects, such as cracks in the glass or plastic. If the housing on the heater cracks or the heater does not heat the pot of water, return it to the store or manufacturer for a replacement. Make sure the cord to the aquarium heather is hanging below the plug-in and other electrical sources (this is in case aquarium water drips down the cord). A string can be tied to the cord loop holding it below the plug-in and other electrical sources.

Things You'll Need

  • Large pot
  • Water
  • Thermometer
  • Submersible aquarium heater
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