The Best Way to Clear Green Fish Pond Water

Unicellular algae are the main cause for green fish pond water. Apart from looking unsightly, algae consume oxygen and thereby compete with the pond fish for this essential commodity. Algae require sunlight and nutrients in order to thrive. These nutrients come from the metabolic waste of fish. For this reason, feed the fish sparsely and don't overstock the pond. Although you can use algaecide to control green fish pond water, opt for long-term solutions such as adequate biological and mechanical filtration and the incorporation of an ultraviolet sterilizer.

Things You'll Need

  • Pond filter, rated for the pond size
  • Pond pump
  • Mechanical filter material
  • Biological filter material, including bio balls
  • Ultraviolet sterilizer
  • Water lilies
  • Commercial algaecide
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Instructions

    • 1

      Install a filter that is rated for the number of gallons that your pond holds.

    • 2

      Include mechanical filter material within the filter compartment. This mechanical filter material typically comprises mats of closely woven material, which physically traps debris and detritus, including decaying aquatic plants and algae.

    • 3

      Include biological filter material in the filter compartment. This material comprises plastic bio balls or rollers on which beneficial bacteria grow. These bacteria convert toxic metabolic waste into less harmful products. Anaerobic bacteria, which colonise the pores within the plastic balls, remove nitrate (NO3-) from the water. Nitrate is a major nutrient of unwanted algae and its continual removal from the pond will discourage the growth of algae.

    • 4

      Connect a pond pump to the filter. Ensure that the pump is powerful enough to move the volume of the pond through the filter compartment at least once per hour.

    • 5

      Connect an ultraviolet sterilizer between the pond pump and the filter. The ultraviolet light source will destroy unicellular algae that were carried away by the water. This dead mass of algae is then trapped in the mechanical filter material. Remove it by rinsing or replacing the filter mats on a regular basis.

    • 6

      Include numerous water lilies in the pond. The broad leaves will shade the water and prevent direct sun light from shining onto the water surface. Algae requires light in order to flourish and will die in poor light conditions.

    • 7

      Feed the pond fish sparsely. Unwanted algae use the metabolic waste of the fish as a nutrient source. By limiting both the initial food source and thereby the amount of waste produced by the fish, algae is easier to control.

    • 8

      Treat the pond with a commercial algaecide as required. Always follow directions and do not overdose.