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Food for thought (2)   (Food for thought 2)


Barley straw – a dangerous substance?
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.

New EU regulations, soon due to come into force, threatens to ban the sale of barley straw or extracts derived from barley straw in the UK as a treatment for algae in ponds.  This is because the straw or its extracts will then be described as a garden biocide. Exemption from this description was granted under the old directive in 1998 which has now expired.

Barley straw reservoirIt is clearly sensible that there are regulations which are designed to look after either our health and safety or the health and welfare of our fish but sometimes a little knowledge is a dangerous thing when rules are written by those with little understanding of the wider picture.

The new directive totally ignores the fact that water companies literally put tonnes of barley straw into reservoirs every year to control algae and this will not be covered under these new rules but pond keepers will no longer be able to put a 100 gram sachet into their ponds in case this presents a danger to the fish in it.

When barley straw is used in reservoirs it rots down and the products of this process obviously are in the water drawn into the treatment plants that provide our domestic water supply. Since the resultant chemical products of the natural organic decomposition of barley straw or of any aquatic plant are not considered harmful, they aren’t filtered out and they form part of all the complicated sounding names of the chemicals listed on the drinking water quality reports that are available to consumers for the water supply in their particular area.

We drink trihalomethanes but what are they?
Barley straw extractIf you have ever seen one of these water reports, have you ever wondered what trihalomethanes are? Simple, they are the compounds formed when the products of natural organic decomposition react with chlorine disinfectants commonly used to sterilise our supplies.  And my water supply authority is legally allowed to supply me with water containing a level of trihalomethanes which will mean that, at the recommended daily rate for human water consumption, I will drink 1 mg of them every four days.

Straw can legally be put into the water we drink in order to control algae and I’m allowed the drink the compounds formed as a result of its decomposition but, if the new directive comes into force as planned, I won’t be able to put them in my pond unless a manufacturer sets up hugely expensive trials to prove that straw is safe!

Water supply authorities won’t have to do this because they can point to the fact that straw has a long history of being used as a “water treatment”. People have been drinking it and no-one has ever been shown to have suffered any ill effects resulting from its use.  Pond owners can’t point to any such history so, if suppliers of barley straw or manufacturers of products containing barley straw extract want to continue supplying those products, they will have prove that it’s safe to put into a pond.

Manufacturers of these products intended for use as pond treatments won’t be able to point to it having been safely in regular use in reservoirs because that use has always been described as a “water treatment” whereas straw for pond use has traditionally been sold as something to prevent algae, i.e. an “algaecide”. Algaecides are classified as biocides so they come under different regulations than something as harmless as a water treatment for water we drink.

Barley strawCould suppliers cheat and pretend that it is used for another purpose?
Once something has previously been described as being for one purpose, it can’t subsequently be redefined as something else in order to get round regulations.  Something that always was an algaecide cannot now be described as a water treatment, which almost makes sense until we remember that we are drinking this strange new chemical in our tap water.

Can they stop us using barley straw in our ponds?  I don’t see how they can. Bureaucrats can pass laws that stop barley being sold as an algaecide but they can’t prevent it growing.  If I decided to grow barley in my garden how could they ban that?  If I decided that an in-ground pond would look best with the barley growing right up to the water’s edge, would I have broken any laws? And when that barley dies back and droops into the water, or the wind blows some straws in, how could a bureaucrat frame a law to make that illegal?

If they can’t stop that from happening by “accident” how can they make a law to prevent barley getting into a pond?  The answer is that they may (or may not) pass a new law to make it illegal to sell barley straw or extracts as an algaecide but they can’t frame a law in such a way as to prevent barley coming into contact with water. So we can continue to use it as long as we either gather it ourselves or we buy it as straw from someone who hasn’t previously sold it as an algaecide.

Keith Davenport, the Chief Executive of OATA, who is championing the fight against this new directive, described it as “bonkers” but needs support for his campaign to make the “experts” see the anomaly in their narrow way of thinking about barley straw. He has prepared some standard letters to send to our MPs and will be able to capitalise on any support when lobbying the Health and Safety Executive who will have responsibility for enforcing the regulation.

The details are on this link:

How does barley straw prevent algae blooms?
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 why 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 metabolise 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 started 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.


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