Research by the "Aquatic Weeds Research Unit U.K." suggests barley straw to
be highly effective in the control of algae. It takes six to eight weeks
for barley straw to become active after it is placed in moving water. After
that barley straw will remain an active algaecide for approximately 6
months. Microbial growth, oxygen and warm water temperatures activate the
decomposition of the straw. With sufficient water flow through the straw,
lignins oxidise into humic acids and, with sunlight and oxygen, destroy
algae, with no effects on higher plant and aquatic life.
Barley straw decomposes slowly so its oxygen demand does not cause problems
unless an excessive amount of straw is used. Stagnant water will go
anaerobic inside the straw bundle killing the microbes.
Barley straw is most effective in shallow (1 m) water with sunlight and
good circulation. Clear water, less straw, but with turbid, muddy water,
and less sunlight more straw is required. Low temperatures are less effective.
Water surface area is used to calculate dosage. In still water ponds the
minimum quantity of straw needed to control algae is 2.5 grams of straw per
square meter of water surface. In water with a severe algae problem, high
first treatments up to 50 g per m2 may be required. Start with small
quantities and monitor effects. You can tie the straw in small bundles or
place it into net bags. Weight or stake them to the bottom in an area with
Adrian R. Tappin
atappin at ecn.net.au
"Home of the Rainbowfish"