Barley Straw Pellets - Best Biological. Barley straw has been processed into a convenient and effective slow release pellet to assist in maintaining a clear pond water naturally. The pellets are completely natural and will support pond growth. It is best to use in the early spring and repeat later in the year if necessary. The English have reported barley straw to be more effective and have a longer lasting effect over other straws such as wheat, linseed and oil seeds. It has been claimed by English research to reduce the growth of new algae. 2.5 pound package will treat 1250 gallon pond. 5 pounds will treat 2500 gallons.