Barley straw is the most popular natural treatment for algae because it works and it’s widely available. You can find straw floats, dunks, pellets, and old-fashioned bales that will all work when sized appropriately. Many pond owners purchase a single floating disc designed to treat a few hundred gallons and are surprised when it has no affect in a pond that’s over an acre in size. Follow manufacturer recommendations and add enough straw to soak up nitrates and produce hydrogen peroxide that interferes with algae growth.
One of the most effective ways to do this is to open a bale and spread it loose over the surface. This shading effect also helps keep algae from reproducing. However, it’s a less than attractive method of treatment. Sinking dunks may work better since they’ll hide on the bottom of the pond out of your view instead. Adding small amounts of hydrogen peroxide designed for pond use can also help, but it’s less safe for fish and easier to apply in ponds without them.
