Fish Tank Underground Filter: Troubleshooting Guide

In order for a fish tank to create a safe environment for its residents, it needs to have biological, chemical and mechanical filtration in place. An underground filter, also known as an undergravel filter, provides all three forms of filtration without a lot of maintenance. This makes underground filters a good choice for both beginning and experienced hobbyists, but it is important to know how to resolve common issues with these filters. When the filter stops working, it no longer provides the filtration that is so critical to maintaining proper water quality.

Things You'll Need

  • Gravel vacuum
  • Air hose
  • Aquarium pump
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Instructions

    • 1

      Check for air bubbles coming out of the top of the underground filter tube. If there are no bubbles, or if the bubbles are very sparse, the aquarium pump may not be working properly. A blocked air tube can also cause this problem..

    • 2

      Remove the air hose from the underground filter and the pump. Check the hose for any kinks or blockages, then reattach the tube to the filter and the pump. If there are still no bubbles, try replacing the air hose. If this does not work the pump will need to be replaced

    • 3

      Clean the gravel bed thoroughly using a gravel vacuum. If the holes in the underground filter become blocked with debris the filter will not be able to work properly. Vacuum the gravel thoroughly to remove any accumulated debris, then check the filter to make sure bubbles are flowing from the tube.

    • 4

      Remove some of the gravel that covers the underground filter and look at the filter itself. If part of the filter is damaged it may need to be replaced, particularly if the plastic is cracked.