Stop Blanket Weed

Stop Blanket Weed

Evolution Stop Blanket Weed

The development of Stop Blanket weed

When Evolution Aqua introduced StopBlanketweed our main objective was to provide a complete solution to combat blanket weed that was safe and caused no harm to fish. The product we have on the market today does exactly what we set out to achieve!

Every Koi keeper and pond owner knows how much of a nuisance blanket weed is. It is a long, thin filamentous algae that can block filters, pumps and pipes, and generally makes your pond look unsightly.

There are many reasons why blanket weed develops in fish ponds, but basically if the algae has exposure to enough nutrients in your pond, in combination with enough sunlight, then it will grow and grow and grow.

It would be natural to assume that by reducing the amount of nutrients in your pond and providing a sufficient level of shade would be enough to get rid of blanket weed, however as every enthusiast knows, things are never that simple.

Safe solution

Evolution Aqua's solution to the problem is a powder based treatment that you mix into your pond water. When added to your pond water, as instructed, the powder is absorbed into the individual cells that make up the weed so quickly that the cell walls are unable to maintain their integrity. The result is that the blanket weed literally falls apart and your blanket weed is stopped in its tracks.

More importantly to us at Evolution Aqua, our StopBlanketweed treatment contains no chemicals that will harm fish, pond water or any other wildlife for that matter.

How to use StopBlanketweed

StopBlanketweed should be added to your pond as soon as you see the first signs of blanket weed forming. We advise that you apply one dose of StopBlanketweed every seven days or until the blanket weed has died. In most ponds this should be about three weeks.

To treat your pond, place 50 grams of powder for every 1500 litres / 330 gallons of pond water in a suitable container. Fill a container with some pond water and mix the StopBlanketweed in thoroughly. Distribute the mixture evenly over the pond surface. If your pond is less than 1500 litres, for example 600 litres, use the following sum:

Pond volume (litres) divided by 1500 x 50 = Powder (grams)
eg: 600 / 1500 x 50 = 20 grams.

For optimum results it is advised that you boost your pond with one dose every month to prevent the blanket weed returning. If water temperature falls below 8 degrees celsius, treatment efficiency is reduced.

The Stop Blanketweed from Evolution Aqua is used in the treatment of filamentous algae, commonly known as blanket weed in koi ponds and garden ponds.
Blanket weed is one of the most hated problems of pond and koi keeping and a nuisance to everyone as it makes your pond unsightly, blocks filters, pumps and pipes. Stop Blanket weed is a unique product which will kill & prevent the regrowth of blanket weed if used as instructed. Stop Blanketweed is easy and simple to use, contains no harmful chemicals and is safe for all pond inhabitants.
Our biggest challenge as Koi and Pond Keepers is to create a 'natural' healthy environment in our ponds, where the correct balance of nitrifying bacteria are encouraged to grow and flourish. The pond and filters in time, will mature to give a balance between fish waste and the filter removing the toxins, If this is not achieved, toxic waste that the fish produce will not be effectively removed and will cause stress to the fish and weaken their immune system. This will lead to a reduction in their ability to defend themselves from potential health problems. Growth, skin quality and development are also adversely affected and in severe cases, fish losses will occur.
Our ponds are often overstocked, over fed and are treated with harsh chemicals to kill parasites, fungal or bacterial infections. All of these have a detrimental effect on the balance of bacteria we are trying to maintain in our filters. Bacterial additives should always be used after any treatments. Even a week on holiday with reduced feeding can cause the bacteria colony to die back. To assist our own eco-system, we can introduce and supplement the correct beneficial bacteria into our system to accelerate and maintain this natural balancing process. This in turn will lead to clear, well balanced water and healthier fish.

Although it's hard to believe there is an advantage in having blanketweed in a fish pond. One of the spin-offs is normally very clear water because the blanket weed is so efficient at removing nitrates that the normal suspended algae don't have much of a chance of growing profusely and the result is clear water.

One other property of blanket weed is that it is a great oxygenating source. When observed closely during sunny days released oxygen can be seen bubbling on the edges of the filaments of the blanketweed. It is the liberated oxygen that allows blanketweed to float on top of the water and create those ugly masses of green string algae.

What makes Blanket weed or String Algae Grow
1. Sunlight is the first condition. Blanketweed is a form of algae which is a plant form and growth is through photosynthesis. This means if there bright sunlight then a good growth condition for blanketweed is met. If the pond is shallow then sunlight can penetrate easily and is even more favourable to string algae growth.

2. Warmer temperatures favour growth of blanketweed so outbreaks are far worse in summer than winter when the problem might disappear completely.

3. Nitrates and Phosphates have to be available in sufficient concentrations to allow the blanketweed to absorb and metabolize. Nitrates are derived from the natural process of denitrification (ammonia to nitrite to nitrate) that takes place in all pond environments by the action of aerobic bacteria within a pond filter. Rain water and municipal water supply is another source of nitrates. Removal of either of these two nutrients will significantly eliminate blanket weed growth. Removal of Nitrate and Phosphate is the main method of most treatments available today.

4. Overfeeding fish. Almost all pond keepers overfeed their fish and this results in concentrations of nitrates being at higher levels and more suitable to blanketweed growth.

What is blanket weed or string algae?
Blanket weed is an alga, it is a relatively primitive form of plant life that is very successful at colonising and dominating an environment under favourable conditions.

Blanket weed spreads and recolonises vegetatively, by branching off and breaking off parts of its own structure which will then colonise new areas. Biologically speaking, this can be a risky strategy, as if the environmental conditions change, it does not have extensive means of adapting to the changing environment. However, where the environment provides consistent conditions, (as in a koi pond), and the blanket weed is adapted to those conditions, it is a very successful strategy, allowing it to thrive and spread rapidly.

Are there different types of blanket weed.
Blanket weed (also referred to as string-algae) is a collective term given to a number of very similar algae that both look and behave identically. The most common genera are Cladophora, Oedogonium and Spirogyra.

Cladophora means 'branched plant' and when viewed under the microscope, it is possible to see the regular-branding filaments, each of which is divided by cross walls. Absorption of light and nutrients is very efficient in such small structures and so growth can be incredibly rapid. They reproduce both sexually (releasing gametes that unite and develop into new plants), and asexually (releasing small motile spores or simply smaller fragments that break off from the main body).

Does it pose any health risks to koi?
We don't resent blanket weed's grip on our ponds because it poses a direct threat to the health of our koi, as in fact, it can actually lead to improved water conditions. When there is a thin, beard-like covering on areas of the pond, koi will browse and graze on the soft, lush growth. However, koi find it less appealing when the beard has grown into lengths of weed several feet in length (hence its other names such as hair or thread algae). Blanket weed will also provide an excellent nursery, both feeding and protecting developing koi fry. If your pond also contains sterlets, blanket weed can prove to be a real hazard for these weak swimmers.

Quite surprisingly, blanketweed is beneficial to a pond in that it will very actively take up minerals and nutrients from the pond water (just like a vegetable filter), the only difference being that this one is in the pond! So vigorous is the growth and uptake of nutrients by blanket weed that should we find a way of confining it to a vegetable filter, it would be our number one plant choice. Unfortunately, like all other weeds, blanketweed does not know its right place and freely enters any koi pond, doing so at its own risk, as its presence is likely to be challenged.

Another redeeming feature is that blanket weed is a very effective oxygenating plant. Its fine filament structure and submerged position lend it to producing a ready supply of microscopic oxygen bubbles. So intense may be its aerating effect that in strong sunlight, rafts of blanketweed will rise up to the surface, buoyed up by the mass of oxygen bubbles caught within its filaments.

What does it need to grow?
Blanket weed is not some sort of aquatic curse that we all fall under for keeping koi. We only have ourselves to blame, because blanket weed will only grow where it finds suitable conditions (these conditions just happen to be similar to the conditions found in most koi ponds). In fact if we wanted to farm blanket weed, we would probably provide it with the same conditions in which it thrives - a koi pond!

The 3 factors that enable blanketweed to thrive.

1. Clearwater that sunlight can penetrate.

It is no coincidence that blanket weed problems have increased in line with the sale and use of UVCs. Mud ponds in which koi are farmed are characterised by their murky water, and even though they represent a nutrient-rich environment, will rarely suffer from blanket weed. Although blanketweed is present in mud ponds, it is out competed and shaded by a combination of the turbid conditions created by the suspended clay and the blooms of single-celled algae. In a filtered and clear koi pond, we have removed the clay and the algae from the equation, leaving ponds exposed and ripe for blanket weed attack and colonisation. The sunlight is required to fuel the process of photosynthesis which allows blanket weed to manufacture food for new tissue growth. By providing clear water conditions for koi we are leaving ourselves exposed to an unhindered blanket weed attack.

2. Nutrients

Algae will readily absorb nitrates and phosphates to satisfy their need for nitrogen and phosphorous as they grow. These are readily available in tap water or indirectly through fish metabolism. Wherever nutrients abound, so will this opportunistic algae, being the first to capitalise on ideal growth conditions.

By killing green water with UVCs, we are perpetuating the imbalance that Mother Nature is trying to fill. The nutrients will continue to accumulate, until an opportunistic algae (such as blanket weed) can take advantage of these conditions. If blanket weed was also susceptible to UVCs then it too, like green water would not be a problem in koi ponds. - Unfortunately it is not.

3. Heat

A warmer temperature will accelerate algae growth considerably and blanketweed growth will be greatest in the shallower areas such as cascades and waterfalls and along the pond perimeter. In winter, the cooler water (and shorter day lengths) prevent blanketweed from growing. Unfortunately, it will only die back, ready to thrive when suitable conditions return in spring.

Why can a pond that has been free of blanket weed suddenly succumb to it?
Even though blanket weed needs specific environmental factors to be in place for it to grow, and these factors are usually unavoidably provided in a koi pond, there are instances when blanket weed will not proliferate in a specific pond.

This can be mystifying as blanket weed is like any other living organism in that it has specific requirements for growth, and will only grow under the correct conditions. So even when two ponds provide these conditions and only one is afflicted by a green plague, it is clear that other factors are coming into play.

Blanket weed does tend to form tougher structure in more alkaline and calcium-rich water, while deeper, shaded ponds that take longer to heat up are less accommodating to blanket weed. What can be even more puzzling is when you have (rather smugly) managed to keep your pond blanket weed-free for years, only for it to succumb this year.

If this happens, try to retrace your steps and look at any of your pond keeping practices that may have changed your water chemistry. Different pond additives, treatments, water sources and food can be the most likely causes of change to a pond that will lead to a blanket weed to bloom.

Does it affect any particular area of a pond?
For the reasons discussed earlier, blanket weed growth can be considerably greater in shallow areas of the pond, particularly waterfalls. Blanket weed will thrive in fast-flowing shallow water, benefiting from the higher light intensity and warmth of water temperatures. Water flow will also 'tease out' the blanket weed encouraging it to grow in greater lengths.

How can you prevent your pond from getting blanket weed?
This is the million-dollar question. For reasons discussed earlier, blanket weed growth is affected and controlled by a number of factors. Blanket weed will find your pond. It is adapted to finding and colonising new environments - so why should your pond be the exception?

The answer to controlling blanket weed lies in reducing one of their 3 key requirements; sunlight, nutrients, and a suitable temperature for blanket-weed growth. As we want our ponds to be as warm as possible (to stimulate koi health and growth), we should look at reducing sunlight and dissolved nutrients.


Sunlight penetration can be reduced in a number of ways. a) Shading. Erecting shading on a pergola will reduce sunlight straight away and reduce blanket weed photosynthesis. It can also help against heron predation. b) Adding dyes. Several blanket weed and algae controls work by adding dark vegetable dyes to the pond, filtering out the sun's rays. This will give the water a tint, and will need to be topped up when the natural dyes are broken down by the filter, but proves effective as a long-term control of blanketweed.

Compelling natural evidence that shading works is evident when a pond suffers from green water. The microscopic single celled algae that turn a pond into a 'pea soup' out compete and shade blanketweed out of its valuable light. Blanketweed and green water have a mutually exclusive relationship, where ponds tend to suffer from either one or the other. Unfortunately, one of the side effects of installing a UVc (which is a guaranteed method of clearing green water), is that blanketweed will proliferate unhindered in the crystal clear, nutrient rich pond water.

Several pond treatments are available that control blanket weed growth by locking up or removing the vital nutrients from the pond water, starving the growth of blanket weed. Upon adding to the pond, they will bind up nitrates and phosphates. Other additives will act indirectly, but achieve the same ends using micro-organisms rather than chemicals to ultimately reduce the nutrient levels in pond water.

Other methods of control.


While all other methods simply control algae growth, the addition of algicides (chemicals that kill algae), work by interfering with vital biological processes. These products are the only ones on the market able to clearly state they kill algae - all others control or reduce it.
Barley straw is a green method of controlling blanketweed and green water. Upon its degradation, which can take several weeks, a cocktail of humic acids are released which react to release hydrogen peroxide, reducing algal growth. To speed this 'natural' process up, barley straw extract is now available.

Electronic controllers.
This method is reported to work on most ponds that have a suitable water chemistry by interfering with calcium ions. This apparently upsets algae metabolism, reducing blanket weed growth.

Top tips for blanket weed control
Adopt the strategy of prevention is better than cure. If you continue to treat blanket weed (which is a symptom of an unbalanced pond) then it will always return, once the treatment has worn off.
Try to determine the factors that are the problem in your own pond:

a. Is it the high levels of nutrients? - Test for nitrates and phosphates.

b. Is it excessive sunlight?

Once you have assessed the dominant factor that is making your pond hospitable to blanket weed, act accordingly: - If the nutrients are high, identify the source(s) of the nitrates and phosphates. (is it tap water?)
Also, for back-up, use nutrient-removing remedies (and re-test your water to see what effect they are having on your pond's nutrient levels).
If your pond is completely plant-free, but suffers from blanket weed, feel free to use an algicide (the only type of product that can claim it kills blanket weed) as there is no risk of affecting other aquatic plant life.
If you prefer a completely natural remedy to blanket weed, use those that offer a 'greener' remedy.

Stop Blanket Weed

Stop Blanket Weed

The Stop Blanketweed from Evolution Aqua is used in the treatment of filamentous algae, commonly known as blanket weed in koi ponds and garden ponds. Blanket weed is one of the most hated problems of pond and koi keeping and a nuisance to...