This is a great natural and environmentally friendly way to kill of the algae and is a popular alternative to chemical pond treatments. A year-round protection that will not harm plants or fish. Float the stick in the pond, ideally placed near the water outlet and tethered just below the surface. When the straw has almost fully decayed, place in a fresh stick then remove the old one two weeks later. The small amount of hydrogen peroxide is released as the straw rots.