Although widley used in the UK and Europe for algae control in lakes and ponds, using barley straw or any other straw for algae control is considered to be a "home remedy" here in the U.S. The use of barley straw has not been recognized, tested or registered by the EPA for use as an algaecide or algaestat. The following information is provided for educational purposes only. In no way should the material be considered legal advice nor is any liability assumed for use of this information. No legal department of any agency has approved the content of these publications.
How Barley Straw Works . . .
As it starts to decompose, barley straw is believed to release a natural chemical into the water which inhibits the growth of algae. These natural chemicals remain in the water for as long as the straw takes to decompose, usually between 4-10 months depending on water temperature. The effects of decomposition has no effect on fish or invertebrates within the lake, in fact oxygenated straw provides a good habitat for fish.
Shoreline Knowledge Base
Algae Control with Barley Straw - Ohio State University
Barley Straw for Algae Control - Purdue University
Using Barley Straw to Control Algae - Rutgers, New Jersey Agricultural Experiment Station
Barley Straw - Penn State Extension
Barley Straw: A Potential Method of Algae Control in Ponds - Maryland Cooperative Extension, University of Maryland
Barley Straw for Algae Control - Delaware Division of Fish and Wildlife