Answer: A natural pond will support a variety of plant life as part of its diverse ecosystem. Usually, a certain amount of grass and other edge plants such as cat tails is desirable. The plants help to stabilize the bank and help keep the nutrient supply in balance. If there are too many of these plants, they can be physically removed. Repeated cutting of the plant tops may starve them out of the pond, too.
If you also have an overabundance of algae, it may be a symptom of an excess amount of nutrients (such as phosphorus) in the water. Sometimes this can be identified and reduced or eliminated by tracing it back to a specific source in the run-off pattern within the pond's watershed. Another tactic would be to introduce some desirable plants which could compete for the nutrients and cover the surface of the pond at the same time. The algae will diminish as it suffers from lack of light and lower nutrient levels.
Gardener's Supply Company (www.gardeners.com; ph# 800/863-1700) sells a product called Bacta-Pur, which helps keep pond water clear naturally.
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