Pond owners looking for a natural solution to cure algae should consider using barley straw. Barley straw gradually releases small doses of hydrogen peroxide into the water, gradually clearing the pond of any algae. Depending on the temperature of the water, and how much algae was in the water initially, this process could take anywhere from 6 to 8 weeks. However, barley straw is an excellent alternative to chemicals because it is completely harmless to fish and aquatic plants.
Purchase a length of netting that has holes large enough to allow water to flow through it.
Put the barley straw inside the net and wrap it in a bundle. You should put between 10 to 100 grams of straw in the bundle for every square meter of surface area. Dirtier ponds will require closer to the 100 gram range while less dirty ponds will suffice with 10 grams per square meter.
Attach a flotation device such as a piece of cork or Styrofoam to the bundle. As the straw gets wet it will sink. Barley straw must have a continuous supply of water and oxygen. The oxygen helps the straw decompose faster, which releases the algaecidal byproducts.
Place the bundle of straw near moving water, if possible, such as a waterfall or fountain.