How to Set Up An Under Gravel Fish Tank Filter

An under gravel filter system is an inexpensive biological filtration method used in freshwater aquaria. Unlike chemical or mechanical methods, a biological system doesn̵7;t use chemicals or artificial filtrates to condition the water. Waste is filtered through plates, where it is broken down naturally. This filtration system allows healthy bacteria and organisms to flourish in the fish tank while keeping waste off the substrate.

Things You'll Need

  • Under gravel filter system
  • Flexible airline tubing
  • Air pump
  • Surge protector
  • Substrate
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Instructions

    • 1

      Choose an under gravel filter system that fits snugly into your fish tank. Under gravel filter systems are sold according to the size of the fish tank. For example, an under gravel fish tank filter for a 55 gallon tank isn̵7;t appropriate for a 75 gallon tank, and a system for a 120 gallon long tank isn̵7;t appropriate for a 120 gallon tall tank.

    • 2

      Thoroughly clean your aquarium. You shouldn̵7;t have any gravel, debris or decorations in the fish tank.

    • 3

      Lay the under gravel filter plates flat on the bottom of the fish tank solid side up with the connectors for the air lines placed along the back side of the fish tank.

    • 4

      Attach the flexible airline tubing to the connectors on the plates. The number of air line tubes you will need depends upon the specific under gravel filter system you choose.

    • 5

      Run the flexible airline tubing up out of the fish tank to the location where you will have your air pump. Mark the appropriate spot on the airline tubing. From that spot, measure six additional inches to allow some slack in the airline tubing. Cut the tubing at that point.

    • 6

      Leave the airline tubing hanging outside of the fish tank. Repeat the process with any additional air lines needed for the under gravel filter.

    • 7

      Thread the flexible airline tubing through the hard plastic tube that stabilizes the flexible tubing in the water. Connect the hard plastic tube to the under gravel filter plate by sliding it into the appropriate hole and turning it clockwise.

    • 8

      Add substrate, such as gravel to your fish tank. The gravel should be at least three inches deep on top of the under gravel filter system. Be sure that the gravel is well rinsed to prevent water clouding.

    • 9

      Place any decorations into the tank. Use aquarium weights for lighter weight decorations that may become dislodged because of the air flow.

    • 10

      Slide the airline tubing onto the connector on the air pump. Plug the air pump into a surge protector. If the air pump has an on/off switch, turn it on now. Some air pumps will turn on immediately when plugged in. You must have the air pump on before adding the water to the fish tank to prevent siphoning.

    • 11

      Fill the aquarium with water. Place any other filters, such as canister filters, or other aquarium equipment necessary, like a heater, into the tank. Add any chemicals needed for your tank, such as chlorine remover or water conditioner.