How to Remove Koi Pond Algae Scum

Algae are single-celled plants found in expanses of water where there is a food source and sunlight. They grow rapidly in koi ponds and the scum they produce float on the surface of the water. Use a chemical algae inhibitor to quickly eradicate the problem, or a natural method of concentrated barley straw extract if you do not want to add chemicals to your aquatic environment. Do not use live barley straw plants because koi like to eat or dig up plant matter in a pond.

Things You'll Need

  • Pond net or rake
  • Chemical algae inhibitor
  • Concentrated barley straw extract
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Instructions

  1. Chemical Method

    • 1

      Remove floating pond algae scum with a net or pond rake, and pull out larger clumps within easy reach of the perimeter.

    • 2

      Choose a chemical algae inhibitor suitable for koi ponds. Some copper-based algaecides are not safe for fish, so read the instructions and warnings carefully and do not purchase a product that could endanger the health of your koi.

    • 3

      Calculate the volume of your pond using a pond calculator, and administer the correct dosage of algaecide following the manufacturer's instructions.

    • 4

      Remove fresh algae scum when it floats to the surface. Chemical algae inhibitors work faster than natural remedies, but the scum may continue to surface for up to a week after you add the anti-algae treatment if the pond is in bright sunlight. Remove any new debris that develops during this time.

    • 5

      Add the anti-algae treatment to your koi pond in a preventative dose during the summer so the scum does not reappear.

    Natural Method

    • 6

      Scoop the algae scum from the pond surface using a pond rake or net. If you can safely reach algae below the surface, pull out as much as you can. The more debris you remove at this stage, the more effective the final result will be.

    • 7

      Mix the concentrated barley straw solution in a watering can at the required dose and pour over the water's surface. Barley straw in liquid form is best for koi ponds so that the fish do not eat the straw in its natural plant form.

    • 8

      Check for dead algae after a week or two and net out any decaying plant matter to keep your water clear. If the weather is warm and your koi pond receives sunlight for most of the day, check for new algae growth until the barley straw begins to work. It may take up to two weeks to become active. During this time fresh algae blooms will develop, so net out any additional pond scum.

    • 9

      Add regular preventative doses of barley straw extract to the koi pond over the summer months to stop algae regrowth.