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Blanket Weed Controllers

Blanket Weed Controller Technical

Blanket weed controller benefits
  • - Relatively low cost blanket weed control solution.
  • - The effect is targeted and doesn’t affect other plants & livestock.
  • - Blanket weed (Spirogyra) is particularly visually unattractive.
  • - Weed chokes the pond and inhibits desired plant growth.
  • - Spirogyra needs very frequent removal if not properly controlled.
  • - No moving parts, fit and forget.
  • - No need for regular refilling or maintenance.
  • - Self-monitoring will indicate any system fault, internally or externally.
  • - Does not effect the chemical composition of the water.
  • - Avoid having to prematurely replace pipe-work, pumps, filters, etc. due to blockage, or avoid dismantling to clean out.


Blanket weed is a common problem in garden ponds. Many pond owners will know too well the challenges and effects blanket weed growth can have on a pond’s natural ecosystem. Aside from its horrible green appearance, blanket weed is a type of algae that can cause many other problems.

What is blanket weed?

Ordinary pondweed, or blanket weed, is a common type of filamentous algae. Belonging to the Spirogyra genus, blanket weed is a string alga that forms into helical filaments. While some forms of algae grow on pond walls, these floating plants tend to stick together to form a gelatinous mass.

Blanket weed thrives best in freshwater systems with a high mineral content and sunlight. Algae spores will grow and cover a pond’s surface under ideal conditions. This green gelatinous mass looks unpleasant and has adverse effects on your pond.

Why is blanket weed a problem?

Blanket weed growth has a significant impact on the pond’s ecosystem. Even the smallest blanket weed blooms can impact your pond if left untreated. Algae can overrun the entire surface of a pond.

When algae cover a pond’s surface, it limits the sunlight and reduces oxygen levels. Aquatic life, such as fish and plants, will soon feel the effects. During Spring, while pond temperatures are lower, alga becomes a dominant ecosystem factor, outcompeting other vital food sources.

Then, during the hot temperatures of summer, algae blooms impact the aesthetics and well-being of a pond’s ecosystem. Blanket weed growth hinders the well-being of fish and aquatic plants by depriving them of essential oxygen and sunlight, as blanket weed growth consumes large amounts of oxygen.

What causes blanket weed?

Blanket weed grows from spores, which are singular reproductive cells that germinate, providing the proper environmental conditions. The wind often carries these spores, so preventing them from entering your pond water is impossible.

If you have a pond, chances are there are algae spores present in the water. As you cannot see them, there’s no way to tell until it starts growing. For the spores to germinate, the right conditions must be present. This is sunlight, a water pH above 8.5, and excessive nutrients in the water.

While you cannot control the sunlight (unless you add shading around the pond), you can control the other two factors. High pH levels in pond water can result from lime leeching, fertilisers, or hard water from taps all contribute to high pH levels.

Excessive nutrient content in water is also another factor that contributes to blanket weed growth. Fallen leaves, fish waste, leftover fish food, and decaying and decomposing organic matter can all contribute to a high nutrient content.

Removing blanket weed

Scooping out the blanket weed from your pond provides a short-term fix. Disturbing the algae blooms causes spores to release into the water. This then leads to more blooms later on. You should avoid removing blanket weed until it is dead.

By killing the algae first, you prevent it from releasing spores into the water. While the spores will return in the future (as the wind carries them), it allows you to implement additional preventative methods.

You could lower your water pH by adding vinegar, picking up fallen leaves, and removing dead plants, but such methods require regular attention. Instead, a blanket weed controller provides a much easier and more effective way to prevent blanket algae growth.

Treating blanket weed

A blanket weed controller is a permanent solution to overcoming problematic algae blooms. As blanket weed has a simple cell structure, they depend on the forms of calcium in the water and their balance.

The weed controller unit tips the balance by using a special low-frequency magnetic field that favours a particular form that disturbs the metabolism of Spirogyra. This magnetic field triggers a sudden and rapid spurt in growth activity that it cannot hope to sustain, and the weed dies in the process.

Spirogyra's growth mechanisms and metabolisms differ from pond plants or resident animals. They are, therefore, safe for the other life in and around the pond. Fish and aquatic plants are unaffected by the magnetic field.

Using a time-variant magnetic field affects the reforming of calcium, which, although harmless to humans, is in sufficient concentration within the antenna wound around the pipe. Unlike the static effect of a permanent magnet, engineers tailor this field to optimise the effect using computer-generated waveforms of varying frequencies.

Therefore, this technique adds no additional chemicals to the water, does not affect its natural pH, and retains all beneficial nutrients, gases, and minerals. Fix the device between the pond’s pump and filter for optimal results. Depending on the severity, you may notice the difference in as little as 24 hours.

The device is safe, and you can install it as a quick DIY job. Installation requires no plumbing, leaving the pond’s natural ecosystem undisturbed. Unlike other methods, such as barley straw and submerged oxygenators, a blanket weed controller is much more efficient.

Opting for a blanket weed controller offers these benefits:
   • A low-cost, permanent solution.
   • Uses 3 watts of power (similar to the amount of an alarm clock).
   • Easy to install and fit around the pond’s existing piping.
   • A permanent solution that has no additional costs or requirements.
   • No moving parts that break, and no ongoing maintenance is necessary.
   • Prevents algae blockages in pipes, filters, and pumps.
   • Once the device is operational, you can leave it to work without any control or adjustments.

Blanket weed before and after treatment using a blanket weed controller