Barley Straw Bales Barley straw works to naturally keep pond and fountain water clear—without the need for synthetic chemicals. As it slowly decays, byproducts are released that aid in maintaining water clarity, which are harmless to fish and other plants in the pond. Just drop it in, and enjoy the results! Barley straw may be used at any time, but best results have been reported when starting in early spring when the water temperature is low. Bales should remain floating for maximum exposure to sunlight and oxygen, which aids in the decomposition process and accelerates the pond clearing benefits.