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Removing Algae from Koi Ponds

Updated on July 16, 2014
Photo take by Belinda Cumming. Japanese Koi fish swimming in the pond at Edogawa Gardens, Gosford NSW Australia.
Photo take by Belinda Cumming. Japanese Koi fish swimming in the pond at Edogawa Gardens, Gosford NSW Australia.

It took much time and effort to create the perfect pond. Effort well spent trying to make a beautiful and serene place for your koi to live. It is a place where you can relax and enjoy the beauty of your surroundings.

However, algae can be a common problem for koi pond owners. Sometimes it may seem like a never ending battle that puts a damper on all your efforts. You want to find a way to rid yourself of this burden.

This article explains both green and chemical methods to treat your algae infestation and prevent further algae growth. Depending on what type of algae you are plagued with one solution may be better than others to solve the problem.

Photo taken by Ramasamy Chidambaram. Water lilies - shot at the Singapore science museum
Photo taken by Ramasamy Chidambaram. Water lilies - shot at the Singapore science museum

Green Methods:

Snails love to eat algae so this is a chemical free and eco friendly option. The

Black Japanese Trapdoor Snail is a larger variety of snail. The specie is preferred because they can survive winter in Northern climates.

Snails eat the algae from your plants, pots, and pond walls. They will consume decaying fish food and leaves off the bottom of the pond. Black Japanese Trapdoor snails have a medium to high algae consumption capacity.

They are live bearing snails and only breed a few times a year, so they will not multiply as fast as egg laying snails. Once fully-grown they will be about four inches long.

You will need one snail to every three square feet of pond space to have the desired effect on algae control. You would need approximately twenty snails for a small pond.

Blocking sunlight from your pond is another chemical free way to prevent algae growth. Algae needs the sun to grow. Water lilies and other water plants can prevent the sun’s rays from reaching the bottom of your pond. For this method to be effective you need about 70% surface coverage.

Chemical Management:

Algaecides and water clarifiers are used to manage algae. These are chemicals that can be used in your pond to kill algae and prevent its growth. Algaecides will kill and prevent the growth of all types of algae to a certain degree.

They include chemicals such as simazine, chelated copper, or potassium permanganate. Note that cheated copper may harm plants that get their nutrients directly form the pond water.

Caution must be used when treating your algae problem with chemicals because using too much can result in the death of your koi. These work best as a preventive. Using these chemicals when you have a full-blown algae problem will most likely result in the death of your fish. The quick death of the algae raises the level of ammonia, which decreases the oxygen levels. A decrease in the oxygen level could result in the suffocation of your fish. It is best to use algaecides before your pond becomes green.

If you have a problem with pea soup algae or planktonic algae, you will want to use a water clarifier. There are two types of water clarifiers. One type clumps the algae into lager particles, which can be removed, by the ponds filter or a skimmer. These particles must be removed to prevent further algae problems. The other type of water clarifier starves the algae thus killing it.


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    • homegrowntexasgir profile image

      homegrowntexasgir 4 years ago from Texas

      Thanks for the tip Peter, always good to have another useful tip.

    • Peter Geekie profile image

      Peter Geekie 4 years ago from Sittingbourne

      Dear homegrowntexasgir,

      Thank you for an interesting article. If it is of interest may I add a natural remedy that I use in the UK and that is to use a suitable size bale of barley straw in the water. This will remove algae and clarify the water.

      Kind regards Peter

    • homegrowntexasgir profile image

      homegrowntexasgir 5 years ago from Texas

      @andamouse Thanks for pointing that I out, I fixed it :)

    • profile image

      andamouse 5 years ago

      It is not "cheated" copper, it's "chelated" copper.

    • PondWorld profile image

      PondWorld 7 years ago from Dallas, TX

      good tips. algae is the number one complaint about fish ponds and boy can it be a problem. I might also add to be sure you have a properly sized and functioning filtration system also. Good mechanical and biological filtration will keep those excess nutrients under control that alge love so much.

    • caninecrtitics profile image

      caninecrtitics 7 years ago from Massachusetts

      I love snails especially apple snails even though they are egg layers they are great for algae control. I love writing about ponds.

    • johnsocrates profile image

      johnsocrates 8 years ago from Kalibo, Aklan

      Indeed a good promotion to prevent these harmful elements out in the dwelling place of this wonderful koi. nice products featured too. you can also try

    • profile image

      Elise 8 years ago

      A very good product for getting rid of all kinds of toxins and algae is Calcium Montmorillonite, or "ionic clay minerals" - for example TerraPond products from California Earth minerals. ( )

    • cipon profile image

      cipon 9 years ago from Malaysia

      Nice tips.I will definitely snails into my koi's pond after this.You win my vote.;-)