Barley-Straw Logs

Nature's Answer to Algae

If you are struggling with green algae in your pond: barley-straw logs are a safe, effective, inexpensive and ecologically sound solution to regain control of the water quality and establish a balanced eco-system without risk to wildlife or plants.

Who uses it

Recommended by the Centre for Aquatic Plant Management, barley straw treatment for ponds is a natural solution for blanket weed and algae problems. It has been widely used since the early 1990s in England for controlling algal growth in canals, lakes and reservoirs and unlike chemical treatments is harmless to pond-life and higher plants.

How it works

Barley straw works by preventing new algal growth, rather than by killing algae. This makes it safer to use than algaecides. Mass-death of algae can have a devastating effect on water quality and can make oxygen levels drop sharply to the point where it can even kill fish. With barley straw the algae simply dies off naturally and is not replaced (or is replaced more slowly) by new growth so that the algae decreases to a new stable level.

In shallow ponds other water plants can establish themselves as the algae is eliminated. As these establish themselves they absorb the nutrients that algae needs and help your pond to achieve an ecological balance without risk of excess algae.

Barley-straw log after three weeks

A small barley-straw log in a pond after approximately three weeks. Although the water is still greenish, the plant-pot can clearly be seen resting on the bottom. When the barley-straw was first added the pot could not be seen at all through the 'pea-soup' of algae.

How to use it

Tether the log just below the surface of the water, preferably near to moving water such as a fountain, otherwise as close to the middle as possible. If you use more than one log, they should be spaced so that each is in the middle of roughly equal-sized sections of the pond. This will keep the treatment circulating evenly through out the pond.

The straw takes about a month to start breaking down. Replace the log about every 4 months. For continuity of treatment keep the old log in the water until the new one becomes active.

If your pond has a dense cover of blanket weed, it helps to rake out as much of this as possible before and for a few days after the barley-straw has been added. This allows the water to absorb oxygen from the air, which is necessary for the barley-straw to start working.

How much do I need?

The growth of algae depends mainly on the surface area of your pond as algae growth is dependent on sunlight. The amount of barley straw needed to start off in still water with should be about 25 to 50 grams for every square metre of surface area. When the algae is under control this can be reduced to 25gms for every square metre and then 10 grams per square metre. Muddy water needs up to twice the amount.

You can use the handy calculator below to work out the right number of barley-straw logs needed for your pond.

Excess barley straw is not harmful until you add at least 100 times the recommended amount, at which point the decomposing straw begins to use up too much of the oxygen in the water.


Barley-Log Calculator
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About our logs

Moon Fern's Barley-Straw Logs are approximately 8 inches long, between 3 and 4 inches in diameter and contain approximately 65 grams of barley-straw. The barley-straw is loosely packed in net bags to allow water to flow through easily.

You can expect results in six to eight weeks for most algae, but blanket-weed can be more persistent and you may need to continue to remove some growth by hand for a while.

Barley-straw logs do not harm fish or other water-dwellers. They provide a habitat for small invertebrates that feed on some of the decomposition products. These in turn are a source of food for larger inhabitants like fish and newts.

A new barley-straw log

An example of a new barley-straw log by Moon Fern ready for use.

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What are algae?

Algae are very simple plants ranging from single-celled algae like those that turn pond-water green, to the longer strands of blanket-weed and even larger water-plants and sea-weeds such as kelp. They do not have the specialised parts of other plants such as leaves, roots, flowers and rhizoids.

Algae thrive in nutrient-rich waters and, because they grow and reproduce so fast can quickly choke a pond and prevent other plants from gaining a foothold. They tend to do well early in spring or after heavy rains, when the water is rich in disssolved nutrients and while other plants are not fully established.

The science behind barley-straw logs

When the barley-straw is placed in the water it starts to decompose. For the first fortnight or so this is mainly through bacterial action, but after this fungi start to break down the lignin in the the cell walls into soluble forms. These are further broken down both by enzymes released by the fungi and by bacterial action to form fulvic and humic acids which are released into the surrounding water. These products are known as Dissolved Organic Carbon (DOC) and are a natural component of aquatic eco-systems.

Dissolved oxygen in the water and sunlight cause the DOC to undergo a series of changes that causes small amounts of hydrogen peroxide to be formed continuously. Very low concentrations of hydrogen peroxide (as low as 2 parts per million in water) are enough to inhibit the growth of algae.

The bacteria and fungi that are at the root of the process need oxygen to survive and do their work. They take this oxygen from the water, which is why it is important that the barley-straw is not densely packed and is placed to take advantage of any water-flow or aeration that is present in the pond.

Some commercial fish-keepers have reported that fish are healthier and suffer from fewer parasites and improved gill function in ponds treated with barley-straw. This is possibly because the clearer water allows sunlight to penetrate deeper and so improves the water quality to a greater depth.

For more information on the science behind barley-straw logs there is an excellent leaflet published by the Centre for Aquatic Plant Control