How to Treat Algae in Unfiltered Pond

Algae are an inevitable problem for outdoor ponds, particularly those that are unfiltered. These little green pests are actually a type of plankton that not only turn your pond water an unattractive tinge of green but can also suck up oxygen that would otherwise be used by your fish. There are many chemicals, known as algaecides, which readily destroy algae in your pond, but there's a better, more natural way to clear an unfiltered pond of algae.

Things You'll Need

  • Hose
  • Water lilies
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Instructions

    • 1

      Use a hose to create a siphon in the pond by thrusting it forward and backward underwater, which will begin draining the water.

    • 2

      Drain about one-third of the water from the pond.

    • 3

      Refill the pond with fresh water, making sure that the temperature approximately matches the water already in the pond.

    • 4

      Scatter water lilies over about two-thirds of the surface of the pond. These will block sunlight and absorb nutrients that the algae would otherwise use to propagate.