How to Make Your Own Nitrate Filter for an Aquarium

Nitrate filters work by allowing tank water to slowly flow through layers of nitrate-absorbing resin balls, or bio-balls. These resin balls remove the nitrate from the water with the help of anaerobic bacteria that occurs naturally in tank water. You can make your own coil denitrator filter for your aquarium and use it to filter out harmful nitrates from fish waste.

Things You'll Need

  • 1 S&D PVC pipe, 2 feet long by 4 inches wide
  • 75 feet 1/8-inch tubing
  • 2 large clips
  • 2 4-inch PVC end caps
  • 4 plastic hose 1/4-inch-to-1/8-inch male adapter check valve
  • 1 flange valve with handle, 1/4 inch
  • Plumber's tape
  • Drill
  • PVC cement
  • Aquarium-grade nitrate-removing resin balls
  • 4 plastic round scrubbies
  • Aquarium pump air tubing
  • 1-1/8-inch tubing, 2 feet
  • 1-1/8-inch tubing, 2 inches
  • Aquarium powerhead
  • 2-1/8 inch tubing, 4 feet
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Instructions

    • 1

      Wrap the 1/4-inch tubing around the outside of the 4-inch S&D PVC pipe to make a coil with the tubing. Carefully remove the tubing from the outside of the pipe and keep it coiled. Slowly insert it into the interior of the PVC pipe, taking care to keep it in the coil shape as you do so. Attach each end of the tubing to an end of the PVC pipe with a large clip. The coiled tubing will force the water to slowly spiral down through the interior of the pipe.

    • 2

      Drill a 1/4-inch hole through the side of each PVC end cap, 1 inch down from the top. Drill a 1/4-inch hole through the top notch of both end caps. Drill another 1/4-inch hole on the side of one of the end caps, 1 inch down from the top, positioned at a 90-degree angle to the first drilled hole. This is for the air bleed flange, which allows you to release excess nitrogen that may become trapped in the pipe.

    • 3

      Wrap plumber's tape around the threaded ends of the four 1/4-inch-to-1/8-inch male adapter check valves and the 1/4-inch flange valve. The white plumber's tape ensures that a good seal is formed when you insert the adapter check valves into the pipe end caps. Insert one adapter check valve, threaded end first, into each drilled hole on the side of the end cap and on the top notch of each end cap. Insert the threaded end of the flange valve into the second drilled hole in the top end cap.

    • 4

      Apply an even layer of PVC cement to the interior of the PCV end cap and slide it onto one end of the PVC pipe.

    • 5

      Place a plastic scrubby down into the PCV pipe so that it rests against the cemented PVC end cap, and sits in the middle of the pipe between coils of the tubing. Add one quarter of the aquarium-grade nitrate-removing resin balls and then place another plastic scrubby into the pipe. Continue alternating between resin balls and scrubbies, ending with the last scrubby.

    • 6

      Use the PVC cement to affix the other end cap to the PVC pipe. Place it so that the 1/4-inch-to-1/8-inch adapter check valves located on both end caps are facing the same direction.

    • 7

      Insert the 2-foot piece of 1/8-inch tubing into the bottom intake valve of the power head and slide the end over the 1/4-inch-to-1/8-inch adapter check valve located on the side of the bottom end cap. Insert the 2-inch piece of 1/8 tubing into the outtake valve of the power head and slide it over the top 1/4-inch-to-1/8 inch adapter check valve.

    • 8

      Insert the end of one 4-foot piece of 1/8-inch tubing into bottom end-cap adapter check valve. Attach the other 4-foot piece of 1/8-inch tubing to the top end-cap adapter check valve.

    • 9

      Position the filter beneath your sump tank. Submerge the free ends of the two pieces of 4-foot tubing into the sump tank and turn on the powerhead. The water flows into the filter, and, as it descends down through the scrubbies and resin balls, the nitrate is removed by the beneficial bacteria that grows on the resin.