Algae naturally occurs in water features and can overrun a pond, water garden or fountain, making the water so green that pond owners cannot even see their fish. Clearing algae requires a balanced ecosystem. Removing algae physically only works temporarily; without a balanced ecosystem, algae will quickly grow back. Combining a variety of techniques can maintain your water feature's ecosystem and control algae growth.
Remove algae with an algae net; use a pond vacuum for pond bottoms and hard-to-reach areas.
Maintain a clean filter that is the appropriate size for the number of gallons in your water feature. Filter mesh grows beneficial bacteria that eat nutrients out the water, which starves the algae and prevents growth. Rinse the filter mesh regularly with pond water or dechlorinated tap water. Chlorine kills good bacteria that removes debris and algae.
Remove debris from the water feature to eliminate potential nutrients that algae can absorb from the water. Catch debris with a powerful pond skimmer and clean its basket regularly.
Plant waterlilies in plant baskets weighted with rocks and place them at the bottom of the water feature. The lily pads grow to the surface of the water and block out sunlight, preventing photosynthesis in the algae.
Introduce floating plants like water lettuce and water hyacinth. Floating plants (as well as waterlilies) remove large amounts of nutrients from the pond water, robbing them from algae. Confine the floating plants to the area near the filter to easily control plant overgrowth, or cover the water feature with the plants to block sun from the algae.
Add flocculants to the water to make single-cell algae group together in clumps large enough to get caught in skimmer netting or filter mesh. Clean the skimmer and filter more often than usual.
Add commercial algae control products, which contain beneficial bacteria and enzymes, to your water feature to further control algae growth. Follow the label directions for application rates and timing.
Introduce koi and goldfish into your pond to graze on string algae, which looks like tiny hairs and grows on surfaces like rocks.
Avoid overfeeding fish, since this will add wasted nutrients to the water that the algae will absorb.