Clear and Clean Pond Water
An Organic Solution Revisited
Since the Middle Ages farmers have known of the benefits
of Straw and used it to keep their farm ponds clear and clean. As
a result of research reports issued in recent years, pond hobbyists
have re-discovered the natural benefits of barley straw for keeping
ponds clear. This article will address some of the questions raised
regarding the use of barley, how it works, how to apply barley and
how much should be used to be effective.
While algae is an important source of food and oxygen for life generally,
if uncontrolled in a pond environment it can truly be an ugly sight
until water plants mature and reduce the amount of light penetrating
the water. Algae can also hinder the flow in drainage systems, block
pumps, filters, cause odor problems and even create a health hazard.
Indeed, emphasis on natural methods of improving water quality is
the main reason for searching out safe new ways to control algae.
Mechanical methods do not always work well, and using herbicides
is contrary to good environmental practice.
Recent Reports and Tests
British researchers at The Institute for Arable Crops
Research, Centre for Aquatic Plant Management (CAPM) in England,
recommend applying barley straw to water to control algae. According
to the Centre, their method "has been tested in a wide range
of situations and in many countries and has proved to be very successful
in situations with no known undesirable side effects." Further
research suggests that lavender stalks, in combination with barley
straw, enhances the effect of the barley straw and is particularly
beneficial in ponds with pumps.
According to Susan Robins’ research article, Washington State
University, Master Gardener, "the success of barley straw and
lavender has been experienced in local San Juan Island ponds where
it has been placed as a test.
Research at the San Juan Island ponds has found that lavender in
combination with barley can be even more effective in the well-oxygenated
water commonly found in ponds with pumped water circulation and/or
fountains. Blending barley straw with lavender stalks in various
proportions allows one to cover a range of water habitats from still
lakes to pumped ponds.
How Barley Straw Works
As simple as it sounds, there are some basic rules
to be followed for the method to work. First, an understanding of
how it works is desirable. According to the CAPM, "when barley
straw is put into water, its cellular structure starts to break
down or decompose. A microbial activity process drives this breakdown
or decomposition." It is during this process that chemicals
are released which inhibit the growth of algae.
The decomposition is temperature dependent, being faster in the
warmer waters of summer than in the cold waters of winter. Bacteria
begin by breaking down the Lignin, which is the starchy material
that makes straw stiff, and other cell wall components of the barley.
After about 2 weeks the active microbes change from bacteria dominant
to fungi dominant. As this process continues humus develops, (rotting)
which is then transformed into a humic acid.
The humic acids are referred to as Dissolved Organic Carbon, DOC.
DOC is a natural part of many fresh and saltwater ecosystems. As
the acid leaches into the water it interacts with sunlight and dissolved
oxygen and becomes unstable, decomposing into 2 single oxygen radicals.
Thereafter, the oxygen radicals form a super-oxide radical, which
then forms hydrogen peroxide in water. The hydrogen peroxide is
more stable and long lasting in freshwater. The breaking down process
of the barley then forms a continuous supply of the right form of
DOC whereby the oxidizing agents can be continuously produced.
According to the CAPM, "Concentration of hydrogen peroxide
of only 2 ppm peroxide have been demonstrated to inhibit the growth
of algae." Some reports determined that barley straw might
also act as a clarifier by flocculating fine particles in water.
How to Apply Straw
The CAPM states that the production of anti algal
activity is only produced when the straw is rotting under well-oxygenated
conditions and is near the surface of the water to properly mix
with sunlight and dissolved oxygen. Straw should be loosely packed
to benefit the breakdown process. Bales are too tightly packed and
therefore do not allow for sufficient water movement through the
straw, which will progressively become anaerobic (without oxygen)
and may actually be a hazard.
Pellets sink, break down quickly and can become a mess at the pond
bottom, thus creating the very problems you want to alleviate. Since
the chemicals are only produced near the surface, barley that sinks
or is too tightly packed will have no useful effect. Further, according
to the Center, anaerobic decomposition can produce chemicals, which
actually stimulate the growth of algae because the algae can use
them as a source of carbon.
The production of hydrogen peroxide from the straw and lavender
will continue until the decomposition process is almost complete—a
process that generally lasts about four to six months. Hydrogen
peroxide in low concentrations such as those produced by the above
process has not been associated with any negative effects either
on higher plants or on invertebrate animals and fish.
Although other straws such as wheat and corn stalks have some algaecidal
properties, barley has been found to be much more effective and
to last longer, and the addition of lavender was found to enhance
Time to Effect Results
Once barley straw has become active, which usually
takes between 2 and 6 weeks, the time it takes to become effective
varies with the type of algae. According to the CAPM small single
cell algae, which turns the water green, usually disappear within
6 to 8 weeks of activity. The larger filamentous algae, known as
blanket weeds or string algae can survive for longer periods and
may not be controlled adequately in the first season if the straw
is added too late in the growing season when algae growth is dense.
It is therefore, preferable to add the straw very early in the spring
before algal growth starts. Barley Straw should be replaced approximately
every four to six months or sooner if the straw fully decomposes
before that time.
How Much Straw to Use
The CAPM found that the most important measurement
in calculating the quantity of straw required is the surface area
of the water. The volume of water doesn’t appear to affect
the performance of the straw as might be expected. This is because
the majority of algae growth takes place in the surface layers of
the water and so it’s not necessary to measure the depth of
the water or its volume when calculating the quantity of straw needed.
In still and small pond waters the dosage of straw should be 50
grams (approximately 2oz.) per square meter of water surface area.
Once the algae problem has been reduced, continued additions of
straw should be maintained throughout the year. If the straw starts
to smell, it should be removed and replaced. It is an indication
that there was too much straw for too little water.The re-discovery
of this completely organic and non-toxic solution to an ugly problem
that affects most pond or lake owners is truly welcome.