For years, barley straw has been promoted as a “natural” solution for pond algae control. You might have heard that tossing a bale or net bag of straw into your pond will help keep algae at bay.
While it’s true that barley straw can have some effect under certain conditions, the reality is that it often creates more problems than it solves—especially if you care about your pond’s health, appearance, and long-term water quality.
In this post, we’ll break down what barley straw does, why it’s not the miracle cure it’s made out to be, and better alternatives you can use.
How Barley Straw Supposedly Works
The idea behind barley straw is this:
When submerged in water, barley straw slowly decomposes. This process releases compounds, mainly oxidized polyphenols, that can inhibit the growth of certain algae species. It’s not an algaecide in the legal or chemical sense, but under specific conditions (right temperature, oxygen levels, and decay rate), it may slow algae growth.
However, those conditions are incredibly narrow. Many ponds simply don’t provide the exact environmental factors needed for barley straw to work as intended.
The Problems With Barley Straw
While it sounds simple and natural, barley straw can create significant issues:
1. Slow and Unpredictable Results
Barley straw does not provide instant algae control. It can take four to six weeks for decomposition to begin releasing any active compounds—and that’s assuming water temperatures and oxygen levels are optimal. By the time it kicks in, an algae bloom may already be in full swing.
2. Decaying Organic Matter Adds Nutrients
As straw breaks down, it releases organic material and nutrients (especially phosphorus) into the water. Ironically, this can feed future algae blooms, making the problem worse over time.
3. Potential Oxygen Depletion
Decomposing plant matter consumes oxygen, especially in warm summer months. Low oxygen levels can stress fish and other aquatic life, and in severe cases, cause fish kills.
4. Messy and Unsightly
Loose straw breaks apart, floats around, and eventually sinks to the bottom. This adds to muck buildup, creating more maintenance work and reducing water depth over time.
5. Not Effective Against All Algae
Even under ideal conditions, barley straw primarily targets planktonic (free-floating) algae. It has little to no effect on filamentous algae (stringy mats) or cyanobacteria (blue-green algae), which are often the bigger problems in ponds.
Why People Still Try It
Barley straw’s popularity is largely due to its low upfront cost and the perception that it’s a “natural” fix. It’s also been used historically in Europe for ornamental ponds and canals, so the idea has carried over. Unfortunately, the science shows mixed and inconsistent results, and it’s not recognized as an effective treatment by many aquatic management professionals.
Better Alternatives for Discouraging Excessive Algae Growth
If you want a cleaner, healthier pond without the guesswork of barley straw, consider these proven strategies:
- Aeration: Improves oxygen levels, speeds up natural decomposition of organic matter, and creates an environment less favourable to algae.
- Beneficial Bacteria: Natural bacteria products consume excess nutrients before algae can use them. CWP Pond Cleaner Plus and CWP Muck Remover Plus are the perfect combination.
- Phosphate Binders: Lock up phosphorus, a primary nutrient for algae growth. CWP Phosphate Binder Plus is a fantastic choice to reduce phosphorus levels.
- Proper Plant Balance: Marginal and submerged plants can outcompete algae for nutrients.
Final Thoughts
Barley straw is an outdated, unreliable method for algae control in ponds. While it may occasionally show results under perfect conditions, the risks, like oxygen depletion, nutrient release, and muck buildup, often outweigh the benefits. If you’re serious about maintaining a clear, healthy pond, focus on long-term nutrient management, aeration, and proactive water quality treatments rather than tossing in bales of straw and hoping for the best.