There are several ways to keep your pond or lake clean and healthy without using toxic pesticides or chemicals . Here are some of the methods they suggest: Bioremediation and bio-dredging : Instead of draining, dredging, and refilling your pond or lake, you can try bioremediation and bio-dredging to remove excess nutrients and pollution. Calcium Silicate : This natural and organically certified mineral can control filamentous and planktonic algae growth without harming fish or other aquatic vegetation. It removes excess phosphorus through mineral sequestration, forming calcium phosphate, a stable and inert mineral. With its food source eliminated, the algae dies off. Diatom promoter and Beneficial Bacteria : Clean Streams, Rivers and Lakes use Aquaritin diatom promoter and Beneficial Bacteria in their water treatment programs to clean streams, rivers, ponds, and lakes. These treatments work substantially better with less treatment cost when used in combination with Calcium Silicate. If