- Once the algae is identified, there are a variety of ways to control it. First of all, it's important to understand that light penetration in water and the availability of nutrients needed for the growth of plants stimulates the growth of algae. Because nitrogen and carbon are usually abundant in the shallow areas of the pond bottom, this is where pond algae usually begin. Also, if there is a good amount of phosphorous available in the pond, it will fuel the algae's growth, as well.
- Making shallow areas of a pond deeper is one way in which pond algae can be controlled. If the depth of the water is more than 3 feet, the algae and aquatic weed problems will be controlled. This is effective because the light cannot penetrate the pond bottom's soil because it's too far underwater.
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Algae can also be controlled by limiting the amount of nutrients that go into the pond after heavy rain. Fertilizers rich in phosphorous can contribute to pond algae, if the fertilizer gets carried into the pond by the flow of heavy rain, so planting a strip of shrubs or high grasses with a drainage area can help reduce the runoff that goes into the pond. Trenches that cause a diversion are also a good way to control the nutrients that enter the pond. Dig trenches that carry water away from the pond to control this problem.
Using chemicals is another way in which pond algae can be controlled, but should only be used for serious infestations. Copper-based algaecides are used to control this type of algae. However, you must be careful when using chemicals such as Endothall because it can harm fish and other non-target species when being used to control algae. Be sure to read the label carefully before you decide to use this method of algae control.
