Q:
Not long ago we were at a nursery looking for
something to control our blanket weed problems. The pond expert at the nursery
told us that we could use Barley straw to eradicate the blanket-weed: Can you
tell us something about Barley straw please?
A:
One of the biggest problems for
many Koi keepers or should it be pond hobbyist are the proliferation of
blanket-weed, which thrives in warm and cold waters with a plentiful amount of
nutrients. Like many other algae species, blanket-weed is, cyanobacteria
(Cyanophyta) that really is not a weed or plant at all but bacteria. This
bacterium undergoes a form of sexual reproduction that results in the release
of spores, which is the likely source of contaminated our Koi ponds.
Ultraviolet (UV) sterilization
while excellent for controlling single cell algae, have no effect on the growth
of cyanobacteria. Various chemical treatments are available as liquids like
Hydrogen peroxide, crystals or granules, but they are all only a temporary
solution, as the cyanobacteria inevitably flourishes again once the chemicals
dilutes beyond a specific concentration. Even through these chemicals can be
used for eliminating the bothersome bacteria the spores will still survive to
plague the pond another time.
Barley straw is not useless
folderol, and can be used as a supplementary treatment for Blue-green algae as
it’s most commonly called. It has become more popular today that it was many
years ago, its use in the United Kingdom is more widespread than in the United
States. Many hobbyists misunderstand this natural method of controlling blanket
weed with Barley straw. Barley straw decomposes in
the water through the activity of microscopic bacteria and fungi that produce
Hydrogen Peroxide (H2O2) as a byproduct. It is this that inhibits the growth of
both blanket-weed and green water. Since both the bacteria and fungi are
oxygen-loving species, Barley straw will be most effective in very well aerated
waters. It will take several weeks for the bacteria to establish on the Barley
straw, so this is no short-term remedy for blanket weed. As the release of
Hydrogen Peroxide is based on a decomposition process, tinting of the
water-body-proper and having to monitor water routinely for pollutants seems to
be its downside.
In cases where cyanobacteria have
an unrelenting embrace on your pond and is making it look unsightly. Other
measures can be taken, but they are admittedly extreme in nature. Another
treatment besides using Barley straw in pond applications is with Hydrogen
peroxide that you can buy from any drugstore. The philosophy behind this
treatment is that hydrogen peroxide acts as an oxidant that damages the cell
walls of the cyanobacteria. Algae and fish produce antioxidants that help
protect them from the destructive nature of hydrogen peroxide. Overdosing
however can damage the gills and respiratory organs of the fish as well as
destroy the beneficial bacteria in the pond. Care must be taken when treating a
pond with hydrogen peroxide. The dose that most pond owners seem to use is 1 to
2 oz. (29.5-59.2ml.) of 3% hydrogen peroxide for every 10 to 15 gallons
(37.85-56.78 liters) of pond water.
Usually only one treatment is
needed but a repeated prescribed amount can be administered far up to two days.
A 30% to 50% water change is highly recommended since cyanobacteria die-off may
cause an ammonia spike.
Editors note:
I just wanted to make a short
comment about the information given in this article. Hobbyists need to
understand that Blue-Green algae or String Algae is really a misnomer for
bacteria that is called Cyanobacteria. Even the name blue-green algae should be
called blue-green bacteria and/or Cyanophyta bacteria.
The name Cyanobacteria comes from
the Greek word kyanós: meaning Blue in color. When you read Syd article
remember that you’re dealing with bacteria and not plant matter as per say.
That is exactly why Hydrogen Peroxide works so well at eradicating these
bacteria. Hydrogen Peroxide is a strong oxidizer that can be compared to
bleach, bleach has a redox of 2000mV. Because it’s such a strong oxidizer it is
a highly reactive oxygen species that when bacteria is exposed to it, they die.
If an overdose is applied to your pond then all plant matter along with
bacteria will suffer and/or die.
Here is another thing that you
may not know, but all obligated and facultative bacteria can catalytically
decompose hydrogen peroxide back into water and oxygen again.
Administering Hydrogen peroxide with a infusion pump, a permeable
membrane bag or drip method to the ponds water will also do the same thing as
Barely Straw will but can be more controlled that that of Barely Straw.
Now you probably scratching your
head about a “permeable membrane bag” filled with hydrogen peroxide and how it
works? Well, the water in our ponds has a higher water potential than the
membrane bag filled with HP and therefore will move into the bag via osmosis
making the bag turgid.
Osmosis is the movement of H2o
(water) from one area of higher water potential to an area of lower water
potential through the permeable membrane bag.
.JPG)
This
photo shows Tolypothrix sp. of cyanobacteria also known as blue-green bacteria.
These bacteria were first classified as plants in 1866 and to this day most
hobbyists still referred to them as plants like String algae, Blanket-weed or
Hair algae but that is a misnomer-they are not!
Photo taken from Wikipedia the free encyclopedia
Koi Appreciation - Barley Straw
The use of barley straw to control
algae in Koi ponds, particularly that pesky string algae, has been talked about
as long as I’ve been around the hobby, but I have never seen or heard a
reasonable explanation of how or why it works, or how to use it. Until now that
is. Reading thru one of my favorite Koi magazines recently – the “E-zine” of
the South East (of England) Koi Club, I came across a very interesting article
by Syd Mitchell. In the article, Syd questions the wisdom of a new EU
regulation which will soon come into effect, which bans the sale of barley
straw or extracts derived from barley straw in the UK as a treatment for
blanket weed (string algae) in ponds on the grounds of being considered as a
“garden biocide” I have not heard of any such regulation in the US, although I
wouldn’t be surprised if something of the sort rears its ugly head here – there
are several EU regulations already being enforced in American industry.
Following an eloquent and persuasive
argument against the regulation, Syd explains, in theory, how barley straw,
when used properly, does what it is purported to do. I would like to thank
Bernie Woolands and the South East Koi Club, as well as Syd, for permitting us
to reprint the following excerpt from this interesting and informative article.
By: Bryan Bateman
From “Barley Straw, A Dangerous
Substance?” by Syd Mitchell, Published in Hotspot, March, 2013
Planktonic or “green water” types of
algae are easily controlled by UV clarifiers. They don’t do anything to the
water to make it in any way hostile to algae; they simply kill any algae cells
that can be pumped through them by exposure to UV light. Filamentous types of
algae, usually referred to as blanket weed, are unaffected because a clarifier
cannot kill any algae cells that don’t pass through it. To counter these forms
of algae, Koi keepers, who prefer not to put chemicals into their ponds,
sometimes use sachets of barley straw.
How does barley straw prevent algae
blooms? – A treat for water nerds.
There are conflicting reports about
the efficacy of barley straw as an algaecide, some say it works, others
disagree and, in the absence of a definitive answer, this is the process by
which I believe it can help prevent algae blooms.
Barley straw, wheat straw and
ordinary hay contain soluble compounds such as carbohydrates and celluloses.
Barley has the most and that’s why it is most often used. When barley straw is
placed in water, heterotrophic bacteria begin to break it down and will
initially be the dominant species in the decomposition process. As these
bacteria metabolized the carbon they need from the walls of the cells in the
straw, a compound called lignin is released. Small numbers of micro fungi that
were present on the straw then begin to break this down too. They proliferate
and take over as the dominant species. The products of all this activity are
humic acid and some enzymes called peroxidases. If these are exposed to oxygen,
as in a well-aerated pond, they form a very weak solution of hydrogen peroxide.
This form of hydrogen peroxide is far too weak to affect fully developed algal
cells so hence the negative story that these products won’t cure an algal
bloom. This makes perfect sense to me because it’s far too weak to have a
detrimental effect on fully formed “adult” algae cells but it is concentrated
enough to have a detrimental effect on “new born” cells by puncturing the new
thin polysaccharide cell walls so that that they lyse, which can roughly be
thought of as the “algae juice” leaking out and the cell bleeding to death.
To me, this would explain why some
say these products don’t work and some say they do. If they are used in a
highly aerated pond just before an algal bloom would have started then there is
a good chance that it won’t happen. If they are used after the algae have begun
to proliferate or in a pond that isn’t at oxygen saturation then they will
fail. Another reason for failure, as with any treatment, may be due to it not
having been used at a sufficient concentration. In the absence of any data from
properly conducted trials, approximate calculations indicate that the minimum
quantity to use in a koi pond is 34 gm per 1,000 gallons with an optimum amount
of around three times that, i.e. 100 gm per 1,000 gallons.
There is no upper limit to the amount
that can be used other than a common sense approach. The decomposition of any
organic material in a pond is aerobic and therefore takes oxygen out of the
system. The oxygen demand at a rate of 100 gm per 1,000 gallons will not be
great and will be well within the capability of a normal Koi pond but
significantly greater quantities will make a significantly greater demand and
should only be used if the water is being highly aerated.
Anoxic Filtration System ®
February 02-2005-2013
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