A natural algae control for ponds. It controls algae by decomposing and producing a continuous supply of hydrogen peroxide into your pond. This will inhibit the development of new algae cells. The Barley Straw doesn't kill algae, but it will prevent it from growing. If algae is already a problem you can still put in Barley Straw, it will take several weeks for the water to react and start to clear. The Barley Straw come in a net bag and should be placed in a location where water will flow though it.