POND SHADING OR DYE -
Prevent Algae and make the fish stand out. In garden ponds we apply very early, even on ice to prevent algae start up while we wait for water to warm up for beneficial bacteria growth. There is no down side to application of this food grade dye.
Shading products, formulated and EPA-registered for aquatic use, do not kill algae or submerged plants directly but limit their growth by reducing the amount of sunlight that reaches them. The United States Food and Drug Administration approved the dyes used in these shading products for food, drug, and cosmetic color additives.
For effective use, apply shading products early in the growing season before plants and algae have started growing. . Adding these products to the water once algae blooms or filamentous algae mats are floating on the water or after aquatic plants are within two feet of the waters surface is less effective. Maintain the dye concentration throughout the growing season for good control of algae and submerged aquatic plants. You may need to add more product every month to maintain the color, or more frequently in areas with high rainfall.