We have a natural drainage pond on our property. Algae forms in the spring and gets worse during the summer. We do not want to use anything that is toxic to animals or plants. What would you recommend treating it with? After we treat this problem we'd like to introduce water lilies.
Algae is a common problem in natural ponds and water gardens. Small amounts of algae are beneficial but these can quickly grow out of control and require some intervention. Keeping the water moving will help introduce oxygen into the water and help manage the problem. Water gardens should have a pump and filter system capable of managing the water volume.
Limiting the light and nutrients available for algae growth is the best preventative solution. Algae populations flourish in nutrient rich ponds. These nutrients come from fertilizer run-off from surrounding areas, fish excrement, decaying plant materials, or fertilizer leaching from potted and fertilized water plantings. Maintain a wide (10 to 20 feet if possible) unmown strip around your pond. The tall grasses and shrubs will help trap nutrient run-off before it reaches the water. The no mow zone also helps keep geese (and their droppings) away form the pond. Regularly remove leaves, decaying plant debris and dead fish from the pond. Avoid excessive fertilization and use of phosphorous containing fertilizers near your pond. Reducing the nutrient sources will help reduce algae problems. Adding water lilies and other water plants will help reduce algae problems. As these plants grow and cover the water surface they block the light reducing algae problems.
Water gardeners have used barley straw to curb algae problems. Research studies have not found it to be a reliable answer. You will need to apply 200 to 250 pounds of barley straw (about 4 to 5 bales) per acre by the end of June. Break the bales into smaller quantities and stuff 7 to 8 pounds of straw into large onion bags or up to 30 pounds in a snow fence. Add a buoyant object to keep the straw afloat. Scatter the straw filled bags throughout the pond and anchor in place.
Photo: Peggy Greb USDA ARS