How to Make a Water Temperature Controller

Home freshwater or saltwater aquariums are fragile environments that require the utmost care to keep the inhabitants healthy. Water temperature can mean life or death for your fish; most tropical and saltwater fish require temperatures between 78 and 82 degrees Fahrenheit. However, due to fluctuating temperatures in your home in accordance with the seasons, the water temperature of your aquarium may also fluctuate, creating an unstable environment and leading to harmful conditions like Ich, an infestation of a harmful parasite whose lifecycle is temperature-dependent. Luckily, with a quick trip to a pet shop and hardware store, you can make a water temperature controller in just a few minutes.

Things You'll Need

  • Aquarium heater
  • Lamp dimmer
  • Aquarium thermometer (digital preferred)
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Instructions

    • 1

      Attach the aquarium heater to the side of the aquarium's interior. It should attach with its included suction cups. Place the heater somewhere where it will be unobtrusive, like in the corner where the fish won't constantly be brushing up against it. The size of your heater will depend on the size of your aquarium; consult the heater's packaging for proper sizing.

    • 2

      Install the aquarium thermometer. Most digital thermometers are waterproof and attach to the interior wall of the aquarium with a suction cup. Other digital models sit outside the aquarium and use an external probe to measure the temperature. You can also use a stick-on thermometer, though these won't be as accurate or as easy to read.

    • 3

      Attach the end of the aquarium heater's power cord to the input plug of the lamp dimmer, then plug the lamp dimmer's plug into a power outlet. The dimmer will restrict the amount of power going into the aquarium heater, allowing you to essentially control the water temperature.

    • 4

      Calibrate the water temperature as you see fit by carefully watching the thermometer as you adjust the power to the aquarium heater until it reaches your desired temperature.