ALGAE REMEDIES Cleaning your Pond Eco-Balance Barley Straw Providing Shade Mechanical Removal Chemicals Download the printable version. Algae is a green plant, albeit microscopic, that needs sunlight and nutrients to survive. Controlling this pondkeeper's bane requires deprivation of either light or food, or both. Be patient Even if your pond is not overstocked with fish, spring often brings a touch of string algae followed by green water...until the pond's plants have fully reawakened. Patience is the key; wait it out as the pond balances on its own. Of course, performing a partial water change may temporarily alleviate the algae bloom (also see Spring Stress), but until the pond plants are awake and out-competing the algae for the pond's nutrients, the algae bloom will return. A Clean Pond If fish wastes and particulate organic matter, commonly known as silt or muck, accumulate on the pond bottom or in gravel pockets within the pond, you may as well incorporate your own algae business. These organic wastes, through their decomposition and role in the Nitrogen Cycle, supply a continual source of nutrients to the water, fostering continual algae blooms and slimy, string algae. Regularly vacuuming the pond bottom in conjunction with partial water exchanges such build-ups and their resultant algae problems, as does the use of bottom-drain systems. Eco-Balance Although many sources cite a list of quantities of various types of aquatic plants to be stocked in the pond to achieve "eco-balance," even a full-sun pond can remain free of algae with only enough submerged grasses or floating hyacinths to out-compete for the nutrients. One bunch per square foot of water surface of submerged anacharis, Elodea, or hornwort (free-floating-but-submerged Ceratophyllum demersum) will keep the pond water free of algae as long as the pond is not over-stocked with fish. Northern ponds should use Elodea canadensis, which is more tolerant of cold water than the South American native, anacharis. Elodea often breaks dormancy and begins removing nutrients from the water at the same time as traditional algae blooms. It is possible with the proper amount of Elodea to not experience an algae bloom at all. Barley Straw An effective prevention of algae growth is the use of barley straw. Generally most effective at prevention when used from November through spring, it seems to keep the algae at bay during the season with the assistance of aquatic plants. The straw should be removed from the pond before it starts to decompose and begins adding nutrients to the water. Many people include barley straw as a media layer in the bio-filter where it is out of sight. Back to Top	Shading the Water Many botanical gardens attack algae by depriving it of sunlight with water dyes. These dyes shade the water either blue or black. Especially in the early spring, such shading inhibits the growth of aquatic plants. Move them closer to the water's surface until they are established and can survive at normal depths. Shade can also be supplied with surface-covering plants such as water lily leaves and floating plants like water hyacinth. Remember, however, that the pond's primary source of oxygen is at the water's surface. Too much surface coverage can result in low oxygen levels, your fish advising you of the fact by gasping or gathering at the surface and at waterfall entries. You'll need to provide additional aeration and/or reduce the amount of fish in the pond, if you maintain extensive surface cover. Another way to shade the pond surface is with a canopy of shadecloth or lattice. Koi pondkeepers often use this method, which protects the koi's colors and shields them from the view of overflying predators. Northern water gardeners find this method inhibits the growth of many flowering aquatics; Southern water gardeners find the partial shade of lattices protects flowering aquatics from excessive heat and oppressive sunlight. Mechanical Algae Removal Twirling a stick or brush in the water is the best way to rid the pond of string algae. Shutting down the waterfall and using a scrub brush (with no soap or chemicals) satisfies fastidious pondkeepers. Ultra-violet light kills free-floating, green water algae as the cycling pond water flows past it. The algae cells are damaged by the light and die within the pond. Cleaning their debris from the pond bottom prevents it from feeding future algae blooms. UV lights also kill the free-swimming stage of many parasites in the flowing water. To protect the beneficial bacteria in the pond, the UV light is set up after the biofilter in the pond's plumbing scheme. Chemical Controls Do not use chemicals to kill the algae since most algaecides are bases on one of two chemicals: copper sulfate or simazine. Copper sulfate also affects other aquatic plants in the pond, particularly submerged grasses, floating aquatics, and more sensitive water lilies. Simazine is not recommended in the presence of fish. Reprinted with permission from Pond & Garden magazine. March-April 2001 Back to Top