Blanket weed, or string algae, is a problem in many ponds. The blanket weed feeds off nitrates in pond water that is created by other plants and fish. The blanket weed looks like long strings of algae, and if left untended will eventually form a large blanket of string algae across the interior of the pond water. There are several ways to help control and eliminate blanket algae. Use a combination of several methods to keep the water clear of all blanket weed.
Remove the physical strands of blanket weed with a weed-remover tool. Place the tool inside the water and spin it around to capture the strands of the blanket weed. Discard the blanket weed well away from the pond to discourage it from growing back. Repeat this treatment once a week until the algae stops growing due to another control method.
Add a copper-releasing cartridge to the water filter in your pond. With the presence of copper, the blanket weed cannot grow because the copper provides a semi-hostile environment for the algae.
Place a nitrate-removing powder inside the pond. Typically, a pond of 1,000 gallons will require one powder packet every eight weeks to keep the blanket weed away. The powder removes the nitrates from the water, which is what feeds the blanket weed.
Add some blue dye to the pond to discourage algae growth. Algae will not grow as much in dark ponds, so darkening the pond with blue dye will decrease sunlight saturation and reduce the growth of algae in the pond. Add one packet or container of dye per 1,000 gallons of pond water every two to three months.
Add a bottle of algicide to the water every one or two months. Use 354ml. of algicide per 1,800 gallons of pond water. Follow instructions on the bottle of algicide if they vary from the previous ratio.