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Blanket Weed


Aquatic Algae & Weed Control


Aquatic algae & weed are an important part of any freshwater ecosystem, imbalances in that system can facilitate the excessive growth of one or both. Extremely dense growths of filamentous algae and submerged weeds may pose serious problems for fish in the form of nighttime oxygen crashes, as well as interfering with boating, fishing and irrigation.

Often these imbalances are man-made and are a result of the waterbodies function. The management of the subsequent algae blooms or weed growth has become an important role for anyone managing freshwater lakes, ponds, or streams.


Healthy Pond Environments

Ecological balance refers to the state of equilibrium between plants, animals, and other organisms within a pond or lake. In a balanced environment, all species keep each other in check and are better able to withstand and recover from disturbances like weather events, swings in temperature, pollution, or disease. 

Ponds with strong ecosystems are less likely to experience excessive growth of aquatic weed or algae. In fact, reasonable amounts of native pond plant growth may be considered healthy in these environments as they provide essential habitat and nourishment for desirable species. The presence of diverse populations of fish, amphibians, beneficial insects, and other wildlife indicates that a pond ecosystem is healthy.



Biodiversity is the variety of plant and animal life in a particular pond, lake or other waterbody, high levels of diversity is usually considered to be important and desirable. Limited or low diversity of species tends to indicate an imbalance within the ecosystem.

Identifying Aquatic Algaes and Weeds

Select 'Algae' or 'Weed' below to see the most common varieties of each and identify which you have and how to treat it. 

Aquatic Algae & Weed Control

Blanket Weed

Blanket weed or filamentous algae tend to be long, stringy and slimy, they are also...

Planktonic Algae

Planktonic Algae

Planktonic algae are microscopic organisms that showcase a variety of colours ranging...

Blue Green Algae

Blue Green Algae

Blue-green algae naturally occur in lakes, ponds, canals, rivers and reservoirs...

Submerged Pond Weeds

Submerged Plants

Those plants that grow almost entirely under the surface of the water, although...

Duck weed and lillies

Floating Plants

Those plants that are vascular and do have roots, but their roots are not necessarily...

Emergent Pond Weeds

Emergent Plants

Those species that are rooted in shallow water, but that stand upright with the...

Those species that are rooted in shallow water, but that stand upright with the majority of their plant tissue showing above the surface of the water. Typically these species will only grow in very shallow water or along margins and slightly up onto dry land. The growth pattern of emergent plants often limits them to these areas and they are often not an issue in larger lakes or ponds with deeper water, but they can completely dominate shallow shoreline areas and, even worse, destroy hundreds or thousands of acres of wetlands and marsh areas which remain shallow or only slightly wet throughout the year.

Emergent Pond Weeds
Duck weed and lillies

Those plants that are vascular and do have roots, but their roots are not necessarily established in the bottom sediment. These species, whether rooted or not, have most if not all of their leaves and other plant tissue floating on the surface of the water. Floating plants that are not rooted in the bottom sediment tend to be very prolific invaders as they are able to move rapidly and spread quickly over the surface of a lake or pond, and even drift or wash into surrounding waterways. Many invasive floating plants are commonly found in small water features and gardens and will often become a nuisance in nearby lakes and ponds.

Submerged Pond Weeds

Those plants that grow almost entirely under the surface of the water, although they do have the potential to reach the surface. When this occurs, you may also see the tips of the plants grow long enough that they lay over and float on the surface of the water. Submersed plants typically cause the most problems for boating, fishing, and aquatic life, because of the density of their growth, and their ability to completely and quickly dominate any aquatic system in which they are found.

Blue Green Algae

Blue-green algae naturally occur in lakes, ponds, canals, rivers, and reservoirs around the world. They are a type of bacteria, known as cyanobacteria, which can produce toxins that are very harmful to people and animals. They are particularly a health risk during warm summer months when their concentrations increase to form blooms and scums on water surfaces. This can look like wispy green or turquoise paint, green scum, or clumps of green particles. Often these surface scums accumulate along the shore where children or dogs play, or where livestock come to drink.

One blue-green algae check is to poke the scum with a stick, if it breaks into small particles, or irregular-shaped clumps, it is likely to be blue-green algae. If, it has tiny round leaves (about 2-4 mm) it is most likely duckweed. If the stick brings up clumps of hair-like strands or soft tubes, then it is harmless filamentous algae.

Blue-green algae can produce potent toxins that can result in a range of health effects on people and animals. Effects on people encountering toxic scums include skin rashes, eye irritations, vomiting and diarrhoea, fever and pains in muscles and joints. Blue-green algae have caused the deaths of dogs, horses, cattle, birds, and fish across the UK.

Blue Green Algae

If you, or your pet, have become unwell after contact with water that you think may be contaminated with blue-green algae, we’d strongly recommend that you seek immediate medical or veterinary advice. Advice on blue-green algae.

Planktonic Algae

Planktonic algae are microscopic organisms that showcase a variety of colours ranging from light blue, green, golden, black, to red. They exist as either solitary cells or colonies formed by single cells. Winds often carry planktonic algae blooms, causing them to accumulate in pond corners or along shorelines. Increased concentrations may lead to oxygen depletion, triggering consequences like fish kills and natural die-offs. Some species, like Cyanobacteria, harbour toxicity that poses risks to humans, fish, and wildlife.

Blanket Weed

Filamentous algae tend to be long, stringy and slimy, they are also known as blanket weed as they can form extensive thick mats resembling a blanket. The filaments are made up of cells joined end to end which give the thread-like appearance. The filamentous patches are often bright green, but can exhibit browns or yellows and even black – especially if the algae is dying. Small ponds and large lake shorelines can be overcome with filamentous algae due to stagnation or high nutrient load; without proper management, filamentous algae can be detrimental to an aquatic system.

Species Include

Spirogyra, Rhizoclonium and Enteromorpha.

Removal Services

Aquatic Herbicides

Aquatic herbicides are a very effective way of removing unwanted weed growth and are particularly effective against those species seen above surface level, like lilies. 

The use of chemicals, algaecides, herbicides etc, if not used in precise doses or under strict supervision by experts, can have a negative effect on fish, plants and other species. The application of herbicides should be carried out by fully qualified and insured operators. It is likely that an Environment Consent would be required from the Environment Agency to do this. AJS Fisheries staff are fully qualified and insured to carry out herbicide applications.

Aquatic Herbicide Spraying
Aquatic Herbicides

Prevention Methods

Aquatic Algae and Weed Surveys

Information regarding the aquatic environment is essential for sound management decisions to be made. Prior to taking action against algae blooms it would be sensible to get a survey of what algae species are present and in what densities so actions can be taken that are appropriate & effective.


We offer two types of survey carried out by an independent aquatic consultant.


Quantitative Algae Survey

The laboratory assessment of a water sample for present algae. This assessment aims to determine whether your water has any currently or potentially problematic algae.


Cost £50.00

Qualitative Algae Survey

Water samples are assessed for species, number of cells and whether they pose a health and safety threat. These samples are ideal for public venues, water sports operators and for more in depth understanding of algae blooms.


Cost £85.00

Ultrasonic Technology

The WaterIQ Technologies Pulsar™ family of ultrasound algae remediation appliances, designed to stop algae in its tracks

The Pulsar 3400 and 4400 appliances use next-generation advancements in ultrasonic technology, fabrication, and IoT technology to advance the fight against algae. Both feature 360° coverage models, with the Pulsar 3400 covering less distance, making it ideal for applications such as clarifiers, small lakes and ponds, and golf courses. The Pulsar 4400 covers a more significant range and is ideally suited for larger lakes, drinking water treatment reservoirs, and wastewater treatment lagoons. In addition, the Pulsar 3400 and Pulsar 4400 introduce onboard IoT and telemetry support, enabling units to transit data from the water to the Cloud, including the unit’s location and operational status.

Pulsar 4300

Designed for smaller applications with lower range for smaller bodies of water and enclosed applications — but with the same high precision targeting of algae and biofilm.

Pulsar 4400

4400 frequencies target most green, blue-green and some golden and red algae. The 4400 provides the highest targeting precision for high value water resources.

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