Barley straw is popular as an organic alternative to keeping ponds clean of algae.
How It Works
Barclay straw is placed in the pond and slowly begins to decompose. During decomposition the cellular structure of the barley begins to break down, and the rate of breakdown is dependent on water temperature and oxygen content. Beneficial bacteria will work faster in warmer temperatures and well-aerated conditions, so you’ll see faster results from barley in summer compared to winter. After a few weeks in the pond, decomposition changes from being bacteria dominant to fungi dominant, leading to “rotting”.
As fungi eat away at the remains of the barley material, humic acid is produced, which is the first major step towards algae control. As the humic acids leech into the surrounding water it reacts with oxygen and sunlight, becoming more and more unstable and eventually forming a super-oxide radical which leads to hydrogen peroxide.
Hydrogen peroxide is a powerful algaecide, but when produced from correctly dosed barley it’s in a low enough concentration to be safe for fish and still work as an algae deterrent. A concentration of just 2 parts per million (ppm) is sufficient for controlling the growth of algae in ponds, and as hydrogen peroxide is more stable in fresh water compared to salt water, it stays effective for longer and requires less frequent dosing.
To work best barley straw treatment needs 3 things:
- Plenty of dissolved oxygen & aeration
- Be placed close to the surface for sunlight exposure
- Good water quality with low nutrient content (heavy algae blooms have to much nutrient content)
How To Use
Volume does not matter; it is the surface area which is important. It is best at about 10 to 25 grams of straw per square meter of pond area. The straw must be floating on top so the water must be aerated and moving. It will not work in a natural pond with no aeration or moving water.
Barley straw should only be used as a preventative measure
Having large amounts of algae usually indicates excess nutrients, excess waste, or low-aerated conditions. Adding more organic material to the pond, such as barley, would only make the problem worse as it takes so long to become effective. As well as this, as barley straw is reliant on the beneficial bacteria in your pond to break it down, adding it to low oxygen and high waste systems will actually reduces its effectiveness, as bacteria are likely already struggling with the low oxygen content and large bio-load present.
The best way to use barley would be to first eliminate any major algae blooms, and then supplement with straw to prevent blooms coming back the following season.
Safety for fish and plants
Barley straw should be fine for fish and plants. Even though barley decomposes to eventually form hydrogen peroxide, which is toxic, it will be in such low concentrations that fish won’t experience any negative effects.
How Long Does it Work For
Depending on the type of barley straw product you’re using, the quality of your filtration, and how much aeration you have in place, the full decomposition process usually lasts between 4 to 6 months.
How Often Should You Use
For the best results and algae prevention, adding more barley straw a few times a year is good practice to make sure there is always a low concentration of hydrogen peroxide in the water. To ensure there is always a little barley decomposing and producing hydrogen peroxide, we recommend replacing your straw every 4 to 6 months.