Keeping Your Pond Algae Free
There are several basic forms of pond algae: the single-celled plantonic type, which turns a pond brown-green; the filamentatious strands that can move through the water, and the more advanced types of pond algae such as chara and nitella, which take root in the pond bed and colonize the water with their stringy tentacles.
Aside from producing oxygen and food, algae can adversely affect water. Algae blooms can clog pond piping, act as mosquito breeding areas, spoil landscape aesthetics, and be toxic to pets. Eliminating or controlling pond algae is often one of the pond owner's primary tasks. Like all plants, algae thrive on nutrients, and reducing sources of nitrogen and phosphorous discourages growth.
Older ponds which are plagued by algae often benefit from gredging (To eliminate the sedimentary source of nutrients). Maintaining a healthy exchange of fresh water helps infuse the pond water with dissolved oxygen, which accelerates decomposition of nutrients. Mechanical aeration can further improve oxygen levels. Ponds with deep, cool water and steep edges discourage plant growth. Natural and biological controls can also discourage algae. Groass carp is used by some owners to control algae, as are crawfish and various strains of nutrient-digesting bacteria. Nontoxic dyes can be used to shade the water, cutting off the algae's source of sunlight. Chemical algaecides offer pond algae control, although the may kill off fish and other aquatic life.
A new method of controlling filamentatious pond algae uses barley straw submerged along pond shorelines. The rotting straw produces hydrogen peroxide as it decomposes, which kills pond algae. Barley straw has proven more effective than wheat, hay, or grass, and is usually anchored underwater in shallow net bags. To be most effective, pond temperatures should be 40 degrees Farenheit with good dissolved oxygen levels and water circulation. Barley straw works best if applied early int he season and should be replaced every 6 months. Barley straw is available from garden centers in either straw or extract form.
Please see Monitoring Water Quality for more information about controlling pond algae.
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