How Can I Kill Algae Naturally?

Algae appears in garden ponds during spring when fish start to eat again after winter. A sudden abundance of excess waste in pond water provides algae spores with the nutrients they require to grow. Sunlight accelerates the growth process, and algae can choke your pond and filter in a matter of days if left untreated. Natural barley straw preparations are effective and work quickly on affected ponds. Use barley straw as a preventative measure early in the season, before algae takes hold and becomes a problem.

Things You'll Need

  • Pond net or rake
  • Barley straw treatment
  • Watering can
  • Spoon
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Instructions

    • 1

      Dislodge loose algae with a rake or net, and manually pull out any clumps near the water's surface. Remove as much as possible by hand before treatment, and there will be less decomposing matter when the algae begins to die off and sink to the bottom of the pond.

    • 2

      Choose a natural pond treatment containing barley straw. Liquid, powder or raw products are equally effective and safe for use in koi fish ponds. Raw barley straw is sold in tightly-packed bales or bundles. These vary in size, but are small enough to hide discreetly under a rock in your pond, allowing the natural nutrients to leech from the straw into the water. Powdered compounds are often ready to sprinkle directly into the pond or dissolve in water before dosing your pond, and liquid versions must be diluted in a watering can or bucket.

    • 3

      Prepare your chosen barley straw treatment in the watering can, according to the manufacturer's instructions, or sprinkle powder directly onto the pond if required. Make up the solution using pond water, not tap water, and stir thoroughly.

    • 4

      Pour the prepared mixture over the pond, covering the whole surface area. Powdered barley straw may not dissolve completely in a watering can, so agitate the mixture immediately before dosing to spread undissolved crystals evenly across the pond. Remaining powder will disperse once in the pond, and it poses no risk to fish or plants.

    • 5

      Leave the barley straw to work for a week, and net out decomposing strands of algae each day as clumps turn brown or dislodge and float to the surface. Administer regular preventative doses of barley straw once your pond is clear, and continue throughout the summer months. Algae naturally dies off over winter, but the spores remain dormant in your pond. Start a new barley straw treatment regimen in early spring to prevent a fresh algae outbreak.