How to Build Your Own Fish Tank Sub Filter

An aquarium in-tank subfilter is easy and inexpensive to build. Most parts are readily available at your local home improvement center. If your aquarium is not rectangular, it might be hard to find a commercially available filter. If you do find one, it's likely to be rather expensive.

Things You'll Need

  • 1 or 2 aquarium filter power heads
  • Fluorescent lighting open cell diffuser
  • Rigid clear plastic tubing, 3/4-inch diameter
  • Fiberglass window screen
  • Silicone caulk
  • Hacksaw
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Instructions

    • 1

      Start with an empty aquarium. Measure the bottom of the tank and transfer these measurements to the light diffuser.

    • 2

      Cut the diffuser with the hacksaw carefully, because diffusers are made of brittle plastic. Once the diffuser has been cut, test-fit it in the aquarium.

    • 3

      Decide if you will use one or two power heads. If the tank is larger then 20 gallons, it's best to use two power heads.

    • 4

      Remove the diffuser from the tank and cut holes in the diffuser to accept the tubing. Wrap the diffuser in the window screening; this will keep the gravel from falling into the diffuser. Cut holes in the screen for the tubes.

    • 5

      Place the diffuser and screen into the tank, and insert the tubes. Place the power heads on top of the tubes to determine the correct height to trim the tubes to. If the tubes fit too loosely, use aquarium-grade silicone to hold the tubes to the diffuser. Make sure the power head will attach to the side of the tank securely.

    • 6

      Place the desired amount of aquarium gravel in the tank and fill it with water. Adjust the power heads for aeration and the direction of flow.

    • 7

      Clean the power head intakes on a regular basis, and your subfilter should run great for years.