How to Make a Fish Aquarium Filter

Part Construction

• 1

  Cut a length of PVC tube 2 to 3 inches shorter than the distance from the substrate on the aquarium floor to the surface of the water.

• 2

  Select the size of sponge filter you wish to install. Large sponge filters require less frequent maintenance, but take up more space. Balance the size of the filter with the visual appeal in the tank. Smaller filters are less noticeable, but require more frequent cleaning to prevent clogging.

• 3

  Cut the filter sponge to the size and shape of the filter you wish to install in your aquarium. Corner filters should be cut in a triangle shape to allow a tight fit to the edges of the aquarium. Maximize the surface area of the filter by cutting round edges. Cut the height of the sponge to no more than 20 percent of the height of the PVC tube. Hold the sponge next to the bottom PVC tube and mark the height of the sponge on the PVC.

• 4

  Place the sponge in a zip-style bag. Fill the bag with sufficient water to cover the sponge. Freeze the sponge and water.

• 5

  Select a keyhole drill bit slightly smaller than the diameter of the PVC pipe. Remove the sponge from the plastic bag. Drill a hole through the frozen sponge in the location the pipe will reside. Thaw the sponge under warm water, squeeze the water out and allow the sponge to dry.

• 6

  Drill numerous holes between the bottom of the pipe and the mark on the PVC with the 3/8-inch bit. This will allow water to be drawn into the PVC pipe when inserted into the sponge.

• 7

  Embed the eight small rocks in a silicone plug at the bottom of the PVC pipe to add weight. The slightly buoyant sponge will be weighed down in the water by the PVC plug. Fully cure the silicone, according to manufacturer instructions, before placing in the aquarium.

Installation and Operation

• 8

  Coat the outside of the pipe, between the bottom and the mark on the PVC, with a thin layer of silicone.

• 9

  Press the pipe into the hole in the sponge, until the pipe and sponge are level on the bottom. Allow the silicone to fully cure before inserting into the aquarium.

• 10

  Connect the aquarium air line tubing to the air pump.

• 11

  Position the PVC pipe and attached sponge in the aquarium. Insert the free end of the air tube into the PVC pipe until it reaches the bottom.

• 12

  Turn on the air pump. Bubbles displace water in the tube to create a suction effect. Water will be drawn through the sponge into the tube. The suction effect will not be sufficient to capture fish against the edge of the sponge.

• 13

  Allow the sponge to operate for 4 to 6 weeks before the first cleaning to allow beneficial bacteria time to grow.