How to Make a Sponge Filter for a Cichlid Fry Tank

Filters that take up less space inside the tank have mostly supplanted sponge filters in most fish tanks, but sponge filters still find use in several utilitarian types of fish tanks. In particular, these filters are very useful in breeding tanks with fry (baby fish) present. First, these filters have no chemical filtration, and as such do not affect medications and tonics. Even more importantly, these filters do not create enough current to injure or trap fry, unlike most modern filters. Additionally, it is extremely easy to make these filters with a bit of know-how.

Things You'll Need

  • Open-cell foam
  • Plastic container
  • Drill
  • 1/8-inch bit
  • Undergravel filter lift tube
  • Dry erase marker
  • Lift tube cap
  • Aquarium glue
  • Shale
  • Airstone
  • Airline tubing
  • Adjustable air valve
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Instructions

    • 1

      Cut your foam into your desired shape. Most commercially available sponge filters are cylinders, but cubes and triangular shapes for corners are also common.

    • 2

      Place your foam into a cheap plastic container. The container must be large enough that your foam can fit inside it without scrunching.

    • 3

      Cover your foam with enough water to submerge it. Squeeze out all of the air in the filter. Place into the freezer until it is frozen solid.

    • 4

      Drill a hole into the top of the frozen foam completely through the foam. Allow your foam to thaw.

    • 5

      Place your uplift tube into the foam. Slide it all the way through, creating the desired height for your filter. Mark the top and bottom of the sponge on the uplift tube.

    • 6

      Drill 1/8-inch holes every 1/2 inch on the part of the uplift tube that runs through the sponge. Saw the uplift tube 1 to 2 inches above the sponge.

    • 7

      Glue the uplift tube cap on the bottom of the tube with aquarium glue. Glue the cap to a piece of slate to anchor the filter.

    • 8

      Slide the sponge over the uplift tube, covering the hole. Place an airstone on a length of airline tubing with an adjustable valve. The water movement generated by the airstone will pull water through the sponge, taking up debris and giving beneficial bacteria a haven to colonize.