How to Build a Box Filter

Box filters are usually used in lightly stocked small aquariums where there is not a great demand on the filter. Box filters need to build up a layer of beneficial bacteria to be effective, so you should never completely replace the filter media. These filters are easy to make with simple tools, and filter media you can purchase from a local fish hobby store. For effective filtration, you need mechanical, biological and chemical filtration media.

Things You'll Need

  • Plastic food container with tight-fitting lid
  • Small water pump
  • Filter floss
  • Ceramic balls or small glass marbles
  • Granular activated carbon
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Instructions

    • 1

      Punch holes in the bottom of the plastic container. The holes should be about the width of a pencil and you will need to add many of them over the entire bottom. The water will flow into the filter through these holes.

    • 2

      Add the filter floss on the inside of the container and press it gently to the bottom. Filter floss will catch the larger particles of debris that come through the filter.

    • 3

      Fill the nylon mesh bag with a few tablespoons of granular activated carbon and add this on top of the mesh. You need about 1 teaspoon of carbon per 1 gallon of water in the aquarium. Adding more will not hurt.

    • 4

      Add the ceramic balls or glass marbles on top of the mesh bag. Leave enough room in the container to insert the water pump. The balls will provide an area for beneficial bacteria to help remove toxins from the water.

    • 5

      Punch a hole in the side of the container near the top. Leave enough room for the lid. The outlet of the water pump will extend out of this hole.

    • 6

      Close the lid of the box filter, immerse it in the aquarium and turn on the pump. The pump will draw water up through the filter and push it out of the hole in the side.