Is your dam starting to smell? Does it not look right? Have you noticed a lack of fish or other aquatic life recently? If any of these points resonate, as well as the water turning green or murky, or an increase in algae, the likelihood is your phosphorus levels have spiked.
What does this phosphorus spike mean? Over the years, nutrients have quietly and gradually built up, causing sediment and the water column above to become overloaded with phosphorus. This problem won’t disappear by itself. Luckily, there are actions you can take to fix it.
In this blog, we’re diving into the reasons why this might be happening, and why using Biostim PhosFix is the best way to restore your dam to good health.
What Is a Sediment Reset and Why Might Your Dam Need One?
If you want your dam to undergo a sediment reset, you don’t need to worry about digging too deep and dredging everything out. Instead, there is an easy way to neutralise nutrient-rich sediment. And this is particularly useful for helping to eliminate the phosphorus that has been accumulating and re-entering the water over time.
Phosphorus enters your dam from sources like:
- Agricultural runoff
- Fertiliser application
- Animal waste
- Plant and organic matter decay
Once the phosphorus has made its way into the dam’s system, it tends to bind to sediment. In oxygen-rich conditions, this binding is fairly stable. But, when oxygen levels drop, especially during hot summer months when water becomes stagnant, phosphorus breaks free again. It rises into the water column, where it feeds algae and aquatic weeds.
Even if you’ve cut back on fertiliser use or improved catchment management, this process called internal loading creates a nutrient time bomb. It can trigger fresh algal blooms year after year.
How Does Phosphorus Bind to Sediment? And Why Does it Matter?
Phosphorus that ends up in your dam mostly starts to dissolve in the water. It usually comes from fertiliser runoff, animal manure, or decaying plant material. Once it’s in the system, it can either stay dissolved in the water column. Or it can attach to sediment particles.
This binding happens through chemical reactions. In oxygen-rich conditions, iron in the form of Fe³⁺ and aluminium can form stable complexes with phosphate (PO₄³⁻). Phosphorus is locked onto sediment particles at the bottom of the dam by these bonds, which temporarily reduce how much is available for algae to grow.
When there isn’t much oxygen, iron changes form. This makes phosphorus let go of the sediment and go back into the water. These bonds don’t always last.
This process, called internal phosphorus loading, means sediment holds nutrients and slowly leaks phosphorus over time. Even if no new nutrients are entering your dam from the catchment, phosphorus stored in the sediment can still fuel repeated algal blooms and water quality issues.
Why Is Phosphorus So Persistent?
Phosphorus is the nutrient freshwater has the least of. That’s why a small amount can cause big changes.
Unlike nitrogen, which can naturally escape back into the atmosphere, phosphorus tends to stay in the environment. It eventually leaks back into the water after accumulating and binding to sediments over time. It helps algae grow fast when it becomes available again.
When too much phosphorus accumulates, you’ll often see:
- Frequent or persistent algal blooms
- Water that’s green or smelly
- Oxygen depletion that can suffocate fish
- Irrigation blockages
- Toxins harmful to animals, people, and crops
If these issues keep coming back, phosphorus in the sediment is almost certainly the cause.
How Algae and Aquatic Weeds Use Nitrogen and Phosphorus
Algae and aquatic weeds rely on two key nutrients to grow: nitrogen (N) and phosphorus (P). Both are common in animal waste, and sediment buildup. However, algae and weeds use these nutrients differently.
Algae, especially blue-green algae, need phosphorus to grow and bloom. Even tiny amounts of free phosphorus in the water can trigger rapid, explosive growth. On the other hand, aquatic weeds such as filamentous algae or submerged plants usually need both nitrogen and phosphorus.
Why Phosphorus Is the Bigger Threat in Dam Systems
Phosphorus is the nutrient that limits growth in most freshwater ecosystems. When it’s available, it often triggers sudden bursts of algae and weed growth.
Unlike nitrogen, which can be lost from the system through natural processes like denitrification (where it escapes into the atmosphere), phosphorus tends to stay in the water and sediment. It accumulates over time, especially in the sediment at the bottom of dams.
Because of this, even if you control nitrogen well, phosphorus in the sediment can keep causing algal blooms for years unless you treat or remove it.
Too Much Phosphorus: Algae Blooms and Dirty Water
Too much phosphorus causes:
- Algal blooms, especially blue-green algae (toxic cyanobacteria)
- Low oxygen in the water can cause fish to die
- Water quality decline, with murky, foul-smelling water
- Blocked irrigation pipes and less water for animals to use
- Toxin production, harmful to animals, humans, and crops
If your dam has experienced repeated blooms or now struggles to support fish and clean water, it’s likely phosphorus in the sediment is the root of the problem.
The Solution: Bind Phosphorus with Biostim PhosFix
If your dam keeps getting nasty algae, smells bad, or has thick sediment, phosphorus is probably the culprit. To fix this, you need to lock that phosphorus away so algae can’t use it to grow.
Biostim PhosFix is a smart water treatment that does just that. It’s made from a special mix of minerals and good bacteria that grab onto phosphorus in the water and sediment. Once bound, the phosphorus can’t feed algae anymore.
Here’s how it works:
- It finds free phosphorus in the water and the phosphorus stuck in the mud at the bottom.
- Phosphorus sticks together, becomes heavy, and sinks. It stays trapped even when there’s not much oxygen.
- Phosphorus is stopped from leaking back into the water and feeding new algae blooms.
- In just days, you’re likely to notice considerably clearer water, and the effects can last over a year.
- Fish, plants, and all living things in your dam are safe from it.
The best part? Biostim PhosFix lets you fix your dam without digging up all the mud or draining the water. It’s an easy, affordable way to keep your dam clean and healthy for the long run.
Pictured: The results after 1 week of applying Biostim PhosFix
Pro Tip (For Best Results)
For optimal results in dams or lakes that have a lot of sludge, we recommend using Biostim Tablets in tandem with Biostim PhosFix. Biostim Tablets reduce the volume of sludge you have, while Biostim PhosFix binds the phosphorus in the sediment left over. This gives you the benefit of both less sludge and less available phosphorus.
Don’t Let Sediment Sabotage Your Dam
A sediment reset with Biostim PhosFix can make a huge difference. You’ll get cleaner water, fewer algae problems, healthier fish and plants, better water for irrigation and livestock, and long-lasting protection for your dam’s water quality.
Our experts are ready to help you work out what your dam needs. We can easily create a tailored plan to tackle phosphorus for good.
Get in touch today for free advice and shop Biostim PhosFix here to get started.