How to Use Pond Barley Straw for Algae (Does it Actually Work?)

A Guide to Pond Barley Straw & How it Works for Clear Pond Water

Barley straw is an interesting way to clear pond water naturally, and research supports its clarifying properties.

A small amount of algae growth is normal in most bodies of water, and in low quantities it can actually be beneficial to ponds and fish! Algae may grow fast under the right conditions, but the majority of algae species are still plants, and plants provide oxygen, deplete excess nutrients, and provide water filtration. The problem with algae is when the weed is left to grow unchecked, it can lead to massive “blooms” which place a huge amount of stress on a ponds eco-system. As algae die and decompose, beneficial bacteria consume oxygen to break down the harmful substances they produce, which leads to lower oxygen for fish, and less efficient filtration as bacteria struggle to keep up with demands.

Although there are effective mechanical (and chemical) ways to quickly get rid of algae, there has been a push to explore more natural methods to reduce costs, maintenance, and to prevent potential damage to the pond in the long run. Barley straw is at the front of that push! Even though barley cannot remove algae as fast as other treatments, it works as a great long-term control method and can help stop algae coming back in future, which is why it’s becoming more and more popular in the fish keeping hobby.

How does barley extract work to kill algae? (Process explained)

As barley breaks down it forms substances that help control algae growth, such as hydrogen peroxide.

To discover how barley works as an algae control method, we need to dive into the details and take a look at each step of the decomposition process as it enters your pond:

1) Barclay straw, or barley extract, 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”.

2) 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.

3) 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.

Will barley get rid of my algae problem?

Barley straw is a good preventive method, but should not be used for treat large algae blooms.

The effectiveness of barley straw will depend on the amount of algae you have, the type of algae, and how quickly you want it gone! As with many natural methods of control, the turnaround to see results is often much slower in comparison to mechanical and chemical treatments. If you have a major algae bloom in your pond, and your fish are suffering, opting for a mechanical treatment (i.e., UV Clarifier) to resolve the problem and then using barley as a preventive method is usually the best way forward.

In-fact, in most cases of algae growth, we would first recommend mechanical removal and a pond clean-up before adding barley to the system. 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.

Barley straw works best in high-oxygen, well-aerated, and algae-free ponds as it’s free to decompose quickly and more efficiently. For this reason, we always recommend barley as a preventive measure, and not to stop a huge algae bloom already in place. 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.

Are barley straw clarifiers safe for fish?

Barclay straw in moderate doses is safe for fish, but higher doses can cause issues with water quality.

If dosed moderately, and assuming your ponds water quality is good and there are no current algae blooms, barley straw should be perfectly fine for fish and plants. Even though barley decomposes to eventually form hydrogen peroxide, which is highly toxic, it will be in such low concentrations that fish won’t experience any negative effects.

The main problems that can arise from using barley straw are drops in water quality, which are often caused by adding barley to a pond with low aeration, poor filtration, or high waste. Barley straw is carbon based and organic in nature; no different to leaves, twigs, and pollen which enters the pond and contributes to waste. Just like other organic material, during decomposition it will break down and produce harmful substances, such as ammonia, as a by-product. Beneficial bacteria would need to break this down or it can become a major issue for fish as concentrations rise. Adding barley straw to a pond which is already struggling with high waste problems would only amplify the issues, causing drops in oxygen and a rise in harmful substances.

If your water quality tests are coming back as good, and you have adequate filtration and aeration in place, adding barley straw to prevent algae should be very safe for fish. It will also work much better as there will be more oxygen for bacteria (meaning faster decomposition), and less chance of problems with water condition later down the road.

Barley Straw Vs Barley Extract (Liquid) – Which is better?

Barley can come in a liquid formula which is more concentrated and faster to act compared to physical straw.

When looking to purchase barley for ponds, you’ll likely come across two different products – barley straw and barley straw extract. Both of these work in a very similar way to prevent algae, but the delivery method is different, as well as the speed of action. In general, barley straw is considered more “natural” and works slower against algae as there is less surface area for bacteria to break down the material. The straw would first need to go through multiple steps of decomposition before hydrogen peroxide is produced. This process can take anywhere from 3 weeks, to over 3 months, depending on water temperature and pond conditions.

Barley straw extract, on the other hand, comes in a highly concentrated liquid form and has been optimized for quicker turnaround. After you apply barley extract to the pond, beneficial bacteria will begin breaking it down much faster as it’s already optimized, leading to faster results. The main drawback of using extract over straw is that you need to be very careful with dosing, as the concentrated nature can make it very dangerous for fish. It is also more expensive than physical straw, and some treatments may contain additional chemicals to enhance it’s effects and increase its longevity.

Both barley straw and barley liquid extract work similarly against algae, but since you should not be using barley as a “quick fix” anyway (see above), we’d usually recommend trying the cheaper and more natural physical straw. It may take longer to work, but it’s more cost effective and you’ll need to dose less as it releases substances at a more gradual rate compared to liquid formulas.

Where to Buy Pond Barley Straw (And How to Use it)

When looking at barley straw treatments, there are few things you’ll want to consider before purchasing. Firstly, you’ll want to make sure the treatment is 100% barley straw and does not contain any coating to “enhance” decomposition. You’ll also want to make sure the straw comes in pre-packaged bales, not lose straw, or you’ll have a difficult time dosing your pond. We also don’t recommend pellets, as they often sink and straw needs to be close to the surface to work! Below are some of our recommendations:


How to use Pond Barley Straw for Clear Pond Water (Best Results)

Air pumps work well as aerators to supply large amounts of oxygen to pond water.

Barley straw will only work while decomposing under well oxygenated conditions, and should be left as close to the surface water as possible (floating or shallow shelf) for the best results. It needs to be close to the surface so enough UV light from the sun can penetrate to form oxygen free radicals that eventually end up as dissolved hydrogen peroxide – the algaecide.

To work best barley straw treatment needs 3 things:

  1. Plenty of dissolved oxygen & aeration
  2. Be placed close to the surface for sunlight exposure
  3. Good water quality and bio-filtration (bacteria) for decomposition

When applying barley straw you want to make sure you have a stable aeration source, such as a fountain or air pump, as well as a filtration system to help remove some of the ammonia and nitrites that come with decomposition. If your barley treatment sinks, you’ll want to remove it and place it on a shallow shelf or consider a lighter product (We don’t recommend barley pellets, as most sink!).

Dosage should be per manufacturers guidelines, so you’ll need to read the instructions on the individual product you purchase. Never use more than is recommended as this will place unnecessary stress on your biological filtration, with very little in turns of extra algae removal. If you have liquid barley extract, you should also dose as per the label guidelines. Dissolved extract has the advantage of remaining free-swimming and being in constant sunlight, and you should see results faster in comparison with barley straw.

How long does barley straw take to work in ponds?

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. In warmer months decomposition will happen faster, and in colder months it will be a much slower process. This is because beneficial aerobic bacteria work more efficiently in summer and much slower in winter when the water temperature drops. Hydrogen peroxide will continue to be produced throughout the entire decomposition process, and will gradually leech into water over this period. You should start seeing results from physical barley straw from 2-6 weeks if treated in spring/summer, and 6-8 weeks if treated in autumn/winter.

For barley liquid treatments, results will usually be slighter quicker and the concentration of hydrogen peroxide slightly higher. On average, you should start seeing results within 2-4 weeks during warmer months and 4-6 weeks in colder months.

Remember, barley straw is a preventive method of algae control, not an algae killer, so a good result from barley treatment would be less algae returning the following year. To remove large algae blooms, always use a direct treatment method and only use barley to supplement the process.

How often should you replace the straw in the pond?

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.

Pond Informer (Chris)

Pond consultant and long-time hobbyist who enjoys writing in his spare time and sharing knowledge with other passionate pond owners.

10 thoughts on “How to Use Pond Barley Straw for Algae (Does it Actually Work?)

  1. In the decomposition of barley straw in the pond, does it change the warer’s colour. Because that is what happened to me. Please advise! Thank you

    • Hi Shelley,

      How much barley straw are you dosing? Also, have you tested your water quality for further problems?

      In my experience, water may turn slightly cloudy when using barley straw in the long term, but this is often only when you add too much, too often. I’d recommend running a broad water quality test to check your ammonia, nitrites, nitrates, and KH parameters. Check here for info:-

    • Hi Christine,

      Yep, that should be fine. In-fact, using the Crystal Clear (which is basically just beneficial bacteria) may actually improve your results from barley as there will be more available bacteria to help decompose the straw, resulting in a quicker turnaround of hydrogen peroxide to combat alage!

    • Hi Diane,

      It may work somewhat in the long term, but the problem with barley extract is it requires bacteria for decomposition. There will be much less active bacteria present in a fountain compared to the bottom of a pond, so it likely won’t be anywhere near as effective.

      If you’re having algae problems in a fountain, and assuming nothing drinks from it, simply adding some algaecide designed for fountains should clear up the problem. Alternatively, you could first clean the current algae and then add a non-toxic pond water dye. Water dyes block a large proportion of sunlight, and can help slow the growth of algae. See here for more info:

    • Hi Karen,

      I’m not exactly sure what Viresco Aqua contains, but it seems to be a natural beneficial bacteria supplement, so using it alongside barley may actually improve overall results (i.e., more bacteria = more efficient decomposition).

      It may be worth reaching out to Viresco to be sure, but personally, I don’t think there should be any problem.

    • Hi Kim,

      Most barley straw products intended for pond use have been treated and made safe for aquatic eco-systems. I’d advise against putting any kind of raw straw/grasses straight into a pond, especially if you’re unsure of the origins as it could contain pesticides, chemical residue, or bacteria. Also, when comparing different hays and straws, there is likely a different rate (and possibly mechanism) of decomposition, so I’d personally stick to barley straw products when it comes to pond-use as they’ve been tried and tested within the industry.

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