How to Keep Algae Out of Ponds With Fish

Algae is common in ponds with fish and typically appears as plankton or filamentous algae. Plankton algae is a type of floating algae that turns your water green, and filamentous algae is a string along the edges of a pond. A small amount of algae in your pond can be healthy for fish, as it provides nutrients for them to eat. However, large amounts can spread bacteria and unwanted disease, which is why you should remove algae visible on the surface of your pond.

  1. Remove all algae from your pond using a rake. Make sure to scrape around the sounds and near the bottom of your pond. Be careful not to scrape up any of your fish, and be sure to wear rubber gloves when removing the algae.

  2. Add plants to your pond that will help to compete for nutrients and provide shade to prevent algae from growing. For example, water lilies help to provide shade, and floating plants like water lettuce and water hyacinth absorb nutrients from water.

  3. Add a bale of barley straw for every 1,000 gallons of water within your pond. Spread the straw over the surface of your pond, but don't let it submerge. The straw is safe for your fish and will prevent any recurring string of algae in your pond.

  4. Clean your biological filter and make sure that it is the right size for your pond. Too small of a filter may not remove enough bacteria. Also, try to increase water circulation to help spread remaining bacteria by swirling a net around your pond.

  5. Continue maintaining your pond by removing any dead leaves, dead plants, dead fish or insects. Also, add nitrifying bacteria, such as Bio-Pond tabs or Microbe Lift. You can purchase these tabs at your local home and garden store, and they will help to starve any algae that may try to grow in your pond.

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