How to Control Algae With Barley Straw

The submersion of barley straw, the dried stems of barley grain grass, into freshwater inhibits the growth of some types of algae. Research in both the United Kingdom and the United States provides mixed results on barley straw's effectiveness, as blue-green algae tends to continue growing and large scale use is needed for noticeable results. Barley grass may be effective in smaller ornamental garden pools.

Things You'll Need

• Tape measure
• Barley straw
• Fabric or mesh netting
• String
• Bricks

Instructions

1. Calculate the surface area of the freshwater body that needs treatment. Measure the length and width of the pond or water feature with a tape measure to determine surface area; multiply length times width.

2. Purchase barley straw in small, woven mats or in small tied bales, ready for submersion into freshwater. Loose straw will need to be bent, woven and tied into tidy bundles prior to use in water features. Carol Lemby of Purdue University cites recommendations to use 225 lbs. of barley straw per acre of surface water, or in small water features, 1 oz. of straw per 10 square feet of water surface area.

3. Slowly submerge the barley straw bundle into the water feature prior to the appearance of algae. Rock the bundle to allow for pockets of trapped air to escape. Alternatively, stuff barley straw into a fabric or nylon netting that has less than 1/8-inch mesh and can be tied closed.

4. Allow the straw to fully saturate and remain in the water for three to six months, if water temperatures are above 50 degrees. The bundle may flow uninhibited on the water surface, or it can be sunk to the shallow bottom and weighted down loosely with a brick. Do not bury or smother the straw as oxygen in the water must reach the straw.

5. Expect full effectiveness of the submerged barley straw four weeks after submersion as the fungus that grows upon the decaying straw reaches great numbers. This fungus releases chemicals that inhibit algal growth.

6. Replace the barley straw after six months in the water with fresh bundles of straw, repeating steps 1 through 4. If water temperatures are below 40 degrees, do not repeat the treatment.

Tips & Warnings

• Barley straw in the United States is not sold as "algae control" because of EPA definitions, which technically makes barley straw a pesticide. Look for it as a "home remedy" in aquatic sections of garden centers and pet supply stores.

• Muddy water reduces the effectiveness of the barley straw.

• In ponds already infested with algae, barley straw acts to prohibit further or new growth, not kill off already present algal organisms.

• Remove barley straw from water after six months, as its effectiveness diminishes and further decomposition of the straw can foul water and add nutrients that will be used by growing algae.

References

• Purdue University: Barley Straw for Algae Control