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How to Prevent Algae in Fish Ponds

By Jennifer Loucks ; Updated September 21, 2017

Algae growing in a backyard pond spreads quickly and takes on the appearance of green pea soup when it gets out of control. In addition to its unsightly appearance, excessive algae will kill the pond's aquatic plants and wildlife. Growth is stimulated by an increase in nitrates and phosphates, lack of filtration, decaying debris and an increase in water pH. Proper pond maintenance and equipment is the best prevention against the growth of algae.

Construct the pond so that it has different depth levels. Providing sloping levels in the pond will assist with debris clean-up and removal, as it tends to collect in the lower areas of the pond.

Provide a 10- to 20-foot strip of woody plants and herbs around the pond that does not require mowing or fertilizing. This will deter nutrient and fertilizer run-off from your yard into the pond.

Add actively growing, underwater aquatic plants to the pond, as they use nutrients in the water for growth. Including these plants in the pond will decrease the amount of food source available for the algae.

Plant water lilies and other surface spreading plants in the pond. These plants limit algae growth by blocking sunlight that heats the water and nourishes the algae.

Remove leaves and other foreign vegetation from the pond on a regular basis. Decaying debris increases nutrient levels that result in algae growth.

Rake algae clumps from the pond with a skimmer or leaf rake to remove floating algae.

Place rocks and stones throughout the pond, as they increase the growth of beneficial bacteria in the water. Beneficial bacteria growth works to combat algae.

Feed pond fish the appropriate amount of food. Excess food dropping to the bottom of the pond will increase algae growth because it contains nitrates and phosphates on which the algae feeds. Purchase algae-eating fish if there is a continued or heavy algae problem.

Chemically treat the pond with algaecides when excessive growth becomes a problem. Remove all plant and fish from the pond prior to applying the algaecide, and verify that your pond filtering system is of a type that will remove the resulting dead algae.


Things You Will Need

  • Woody plants and herbs
  • Underwater aquatic plants
  • Pond skimmer
  • Aeration system
  • Rocks and stones
  • Algae-eating fish
  • Algaecides


  • Install your pond away from trees and shrubs that regularly shed leaves.
  • Small amounts of algae in a pond produce beneficial oxygen, which increases the water quality and prevents plants and fish from dying and decomposing in the water.

About the Author


Jennifer Loucks has been writing since 1998. She previously worked as a technical writer for a software development company, creating software documentation, help documents and training curriculum. She now writes hobby-based articles on cooking, gardening, sewing and running. Loucks also trains for full marathons, half-marathons and shorter distance running. She holds a Bachelor of Science in animal science and business from University of Wisconsin-River Falls.