How to Build a Fish Bio Filter

If you've ever owned a fish pond, you know that having a bio filter properly set up is important for clean water. With larger fish and even more fish quantities, bio filters are significant for the well-being of your pond fish. Without a good bio filter, clear pond water will eventually turn into cloudy, waste-filled water, decreasing the chances that your fish will thrive in their environment. Building a fish bio filter is really quite simple and can be done without spending much money.

Things You'll Need

  • Rubbermaid stock tank
  • PVC pipe, 1 1/2 inches
  • PVC tee
  • 3 PVC elbows
  • Threaded nipple reducer, 1 1/2 to 1 1/4 inches
  • Closet flange, 4 inches
  • Plastic egg crate style overhead 2x4 light grate
  • Bolt, nut and washer combination, 1/4-by-1 1/2-inches
  • Filter medium
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Instructions

  1. How to Build a Fish Bio Filter

    • 1

      Determine whether or not the stock tank drain will be in the front or back end of the filter. Most people prefer to keep the drain in the back. Cover the drain plug with Teflon tape, since it won't be used much, and refrain from over-tightening the drain to prevent breakage. Prevent leaks by filling up the tank with water until the water line exceeds the fitting.

    • 2

      Cut out a round hole on the tank's top flat area. Drill mounting holes into the area and when mounting the closet flange, block the filter medium and plants from passing through the overflow with the egg crate grate piece. However, before you install the flange, make sure the flat area is sealed.

    • 3

      Cover the overflow flange with liner material if you want to conceal your bio filter behind a waterfall. Covering the flange reduces the chances that water will release out of the flange and onto the dirt around the pond.

    • 4

      Cut the PVC pipe appropriately so that the tee and elbows can connect. If you want to give your pond a swirl or ripple effect, the bottom elbows must point away from one another. Make sure the other PVC points up toward the sky when you cut it as well. Place a PVC elbow on top of the length pointing upward and put the nipple reducer inside.

    • 5

      Make sure the grate can fit inside the tank by cutting it accordingly. However, if you accidentally cut the grate too short, put two 2-by-4 pieces of grate on the bottom so that the grate is raised. The grate is mainly put into place so that there's space between the filter medium, as well as plants, and the end of the tank. Cut a small circle into the grate's center and fit the PVC pipe facing upward through the hole. Once the PVC pipe is attached, place it inside the tank and lower the grate.

    • 6

      Loosely drop the filter media on the grate so that the filter media is just below the overflow, making sure that you have enough filter media and plants for the capacity of your tank.

    • 7

      Connect the top elbow in place and make sure that the elbow is near the hose that will exit the pond so that you can connect it later. Make sure the nipple isn't loose after you put in the treaded reducer. Then, attach the hose to your pump and you're done.