How to Use Cat Litter for Sand Filter Media in a Koi Pond

Koi are beautifully marked cold water fish, which were selectively bred by the Japanese from common carp. These large and inquisitive fish, which are commonly kept in ponds, require high-quality water. Biological filtration is therefore paramount in koi ponds. Beneficial bacteria cultures, which coat the filtration material, remove the toxic metabolic waste products from the pond. Aerobic bacteria strains develop over the surface of the filter material and convert ammonia into nitrite and then nitrate, the least harmful of these products. Cat litter can be used as the filter material upon which these beneficial bacteria grow.

Things You'll Need

  • Koi filter, including biological filter compartment
  • Cat litter
  • 10-gallon plastic bucket
  • Garden tap
  • Pond pump
  • 10-gallon clean plastic container
  • 2-gallon plastic jug (optional)
  • Wheelbarrow (optional)
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Instructions

    • 1

      Use sufficient cat litter to fill the biological filter compartment of the filter box.

    • 2

      Rinse your hands under warm running water to remove any detergents, soaps and natural body oils. These are all harmful to the beneficial bacteria and koi.

    • 3

      Half fill a 10-gallon plastic bucket with cat litter. Place the bucket under a garden tap and turn on the water. Place your hands in the bucket and stir the cat litter to clean it.

    • 4

      Turn off the tap and carefully tip the bucket to drain the water. Be careful not to pour out the cat litter.

    • 5

      Repeat the process until all dust and debris in the cat littter have been washed away.

    • 6

      Wash enough cat litter to fill the biological compartment of the filter box.

    • 7

      Turn off the pond pump.

    • 8

      Open the lid of the biological filter. Remove the mechanical filter material and place it on a clean surface next to the filter box.

    • 9

      Remove the chemical filter material -- which is typically a number of nylon bags containing activated carbon -- and place into a clean plastic container.

    • 10

      Fill the biological filter compartment with cleaned cat litter if the compartment is empty. If the compartment already contains another type of filter gravel, use your hands or a 2-gallon plastic jug to scoop it into a wheelbarrow. Place the cat litter into the emptied container.

    • 11

      Replace the chemical and mechanical filter material.

    • 12

      Replace the lid on the filter box. Plug the pond pump into a power source and turn it on.