How to Install a Submersible Heater in a Fish Tank

Tropical fish need a heat source to keep their aquarium water at the required temperature. Submersible fish tank heaters stay under the water's surface permanently and usually have some form of thermostatic controller to maintain the ideal environment. Installation involves setting the temperature dial and attaching the heater to one wall of your aquarium. Set up the aquarium heater and stabilize the water temperature before adding fish to your tank.

Things You'll Need

  • Water dechlorinator
  • Submersible aquarium heater
  • Aquarium thermometer
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Instructions

    • 1

      Fill the aquarium with dechlorinated water. Do not artificially heat the water before pouring it into the tank. It is easier to warm up room-temperature water than it is to cool it down to achieve the correct temperature.

    • 2

      Attach a stick-on liquid crystal display aquarium thermometer to the front of the tank, outside, where you can see it easily. Alternatively, if you have a digital thermometer and probe, place the probe in the water and run the cable out through a rear vent in the tank lid. Stick the display unit on the front of the tank with the supplied suction cup or adhesive pad.

    • 3

      Remove the aquarium heater from its box and inspect it for damage. Submersible heaters typically have a heating element encased inside a thick glass or plastic tube. Check that the glass is intact before installing the heater.

    • 4

      Turn the temperature dial or move the slider to the temperature required by your species of tropical fish. Clip the heater into its cradle attachment or attach the suction cups. Some heaters are already assembled with the mode of attachment in place or have integral suction cups on the back of the unit.

    • 5

      Submerge the heater in the tank and attach it horizontally or diagonally on the back wall of the aquarium, near the filter outlet, to circulate heated water effectively. Make sure plants or decorations do not obscure the heater. Heat rises, so do not place the heater at the water's surface because this can cause cold spots to form at the bottom of the tank.

    • 6

      Plug in the heater and switch it on. An indicator light remains illuminated until the required temperature is achieved. When the light goes off, check the reading on the outer aquarium thermometer. Adjust the dial on the heater, if necessary, to raise or lower the water temperature. Leave the aquarium to stabilize for at least 24 hours before adding fish.