What Causes Stringy Algae?

Nutrients

• Stringy algae requires nutrients to grow. The greater the level of nutrients in a pond or lake the more algae, both stringy and other types. Phosphorus is a key nutrient in algae development and enters water as runoff from fertilizers and from waste treatment plants in addition to natural sources such as plant material. Maintaining a proper balance of phosphorus is important. Too little, and there will not be enough algae. Too much algae, and the strings will choke out life in the pond or lake.

Temperature

• Warm temperatures produce string algae. Summer and early fall presents the right combination of warm weather and nutrients to stimulate stringy algae growth. String algae on top of water present problems for boaters and recreational uses of lakes. Unlike other algae, string algae is removable by hand, according to the State of Washington's Department of Ecology. This method only works in small areas and the strings regrow quickly.

Sunlight

• String algae requires sunlight to grow. It uses photosynthesis to produce carbohydrates. Transforming the energy from the sun into nutrients for a pond or lake not only makes string algae grow but provides for a continuation of the aquatic life cycle. The more exposure a pond or lake has to sunlight, the more the string algae will grow.

High pH

• Water with high pH, or acid, promotes the growth of stringy algae. One way to reduce stringy algae in a pond is to lower its pH level. Levels of pH need to range from 7.5 to 9.5, with the higher number producing the lowest amount of string algae. Any number higher than 9.5 is too acid. Test your pond or lake. If the pH level is too high, explore options to lower the level.