How Barley Straw Works to
Control String Algae
Water gardens and small ponds tend to be especially susceptible
to water quality problems. They are shallow and warm, often low
in oxygen, and are usually in a landscaped setting where fertilizers
and organic materials run off and settle in the pond. The result
is a water feature, intended to be beautiful and soothing, that
is lost to the high maintenance required to keep it clean. Finally,
the pond owner resorts to expensive,
short-lived chemical treatments in the hopes of seeing
that prized koi, hiding just inches below the surface.
Today's alternative, barley straw, offers the pond owner a
safe and effective, inexpensive, and long-term solution to string algae control. The pond owner places a small bag of barley straw at the surface
and lets nature do the work. When properly applied, naturally
occurring microorganisms decompose the lignins in the barley,
releasing humic substances (dissolved organic carbon) in the
water. In the presence ofsunlight and oxygen, these compounds
are converted into low levels of hydrogen peroxide. The hydrogen
peroxide is the component that modifies the pond chemistry to
improve pond clarity. Hydrogen peroxide itself is relatively
unstable and does not persist in water, but the slow release
effect from the barley straw provides a constant source of hydrogen
peroxide. The effects from barley straw will begin as early as
one to two weeks after installation, and will remain effective
for between four and six months.
Tips for Success:
Apply early in the spring (March
or April) before algae and turbidity increase.
Physically remove existing algae
at the time of installation.
Float the barley at the surface
for best exposure to oxygen.
Aerate the water.
Place the barley near a waterfall
Use smaller. more frequent applications
in warmer climates.
Apply a second treatment prior
to total decomposition of the first. Also, leave the first application
in the water for at least two to three weeks beyond application
of the second treatment.
Recommended application rates
are based on results as observed at the Centre for Aquatic Plant
Management in the United Kingdom. Performance may
vary by climate, typically with more frequent smaller
doses recommended in warmer climates. Increase the dosage in
waters that are turbid or muddy. Results may vary and it is better
to apply too much straw in the first application and gradually
reduce the dose to an effective maintenance dose.
Effects on other organisms
in the pond:
No harmful effects on vascular
aquatic plants, invertebrates, or higher animals has been observed
in laboratory or field testing. On the contrary, some studies
show improved growth of invertebrates, in turn providing prey
for fish and waterfowl.