The dreaded “pea soup” pond is one effect of algae – in particular the green kind (a site that we are all too used to seeing in gardens up and down the UK). But what about that slimy hairy stuff? Don’t worry - you aren’t the first person to become sick of the site of blanket weed taking hold over your garden pond. If you have clicked onto read this blog you will more than likely be in need of some useful advice in terms of how to control blanket weed. If not, you simply may be looking for advice to share with others who you know will benefit from some guidance. Either way, we have some great tips to consider when needing to reduce the effects and the quantity of blanket weed breaking out into your pond.

Blanket weed is a common freshwater algae. It is a plant that loves warmth and sunshine, so those ponds situated in an area of the garden receiving a lot of sunlight may struggle with controlling this problem more than others. Algae grows through the process of photosynthesis, so if blanket weed spores exist in your pond and sufficient nutrients are available in the water, then the rays and the warmth of sunlight will facilitate blanket weed growth over the summer months. Before the introduction of blanket weed removers, blanket weed treatments and blanket week preventative measures, it would have proved near-on impossible to get rid of this form of algae from a pond.


Luckily, science has served us well in the blanket weed department! Although there are some benefits to having blanket weed in a pond within controlled measures, it is extremely fast-growing! The algae will re-colonise vegetatively and spread by branching its long filaments, often breaking up and re-structuring on its own, which will then colonise in new areas of the pond. A side-benefit of having blanket weed in your pond is that the water will be considerably clear and this is because key nutrients are taken up by blanket weed so efficiently and rapidly, that this will prevent other forms of algae (in particular green algae) from a chance at getting started! There are also different species of blanket weed. In particular, a species named Spirogyra, can have detrimental effects on the health and development of your pond. The tangled pond scum also known as “silk weed” “mermaid tresses” and “water silk” forms dense mats of filaments that float on the surface of the pond during sunny days, kept afloat by tiny bubbles of oxygen arising from photosynthesis. When the sun goes down, the hairy mats sink down into the water and photosynthesis is reduced, causing the strands of Spriogyra to consume oxygen for cellular respiration. This increases the level of CO2 in your pond water creating large fluctuations in the dissolved gas levels of the water. This in turn, can lead to rapid changed in PH levels as well as stress and death to living organisms.


You may be surprised to learn that unfortunately UV filter lights have no effect of filamentous algae (that’s blanket weed) in ponds, leaving just chemical and microbial methods to help with control. In order to get a grip on blanket weed in your pond, it requires a little background knowledge – but you will be pleased to know that it’s all very simple stuff to take on board! Algae are plants that need nutrients to sustain their lifeforce. These nutrients in particular are nitrogen and phosphorous. In pond water these show up as nitrates and phosphates. So no nitrates and phosphates – no blanket weed! The key is therefore to get rid of the nitrates from your pond water with naturally occurring bacteria mixtures such as Nishikoi’s “Goodbye Blanket Weed” – a solution that studies carried out at Leicestershire’s Brooksby college have proven to be the most effective remedy in blanket weed control. The award-winning product which contains a secret mixture of barley straw and bacteria comes in sachet form and requires just 1 dose to be added to your pond filter or directly into your pond every week. The harmless bacteria and friendly-enzymes eat away at the food consumed by blanket weed in your pond to reduce nitrate levels within the water.


Blagdon Blanket Weed Buster is another form of pond treatment. It consists of a 100% natural probiotic blend of bacteria and is safe for all plant species, fish species and other pond inhabitants. Blanket weed buster also contains an added benefit of a Sludge Buster to remove all the dead algae and requires just one level spoon for every 32 litres (or 292 gallons).


There are also a host of other preventative measures that can be taken to control blanket weed in ponds:

Reducing sunlight penetration into your pond water by creating shade conditions around the pond will certainly help! Use a combination of attractive aquatic plants to fill-up exposed areas. Water lilies with their large surface area are a great choice as these will also help to reduce nitrates within your pond water.


Barley straw and barley straw extract take a while to start working but are effective. The addition of barley straw and how this effects blanket weed is fairly complex but is determined by the in-situ production of hydrogen peroxide which in turn, acts as an oxidizing agent and interferes with the process of photosynthesis.


Electronic blanket weed controllers have been claimed to be effective, however the results are sometimes not as long lasting as you would hope for. Algae such as blanket weed can adapt to new surroundings very quickly, thus overcoming the effects of electronic treatments promptly.


If other preventative forms of blanket weed control prove difficult, then a blanket weed remover is an effective method. Designed with prongs that have blunted edges to prevent ripping the liner of your pond, the tool is successful in physically removing the worst of the blanket weed before you decide to add methods such as the Goodbye Blanket Weed solution or Blagdon’s Blanket Weed Buster.


Whichever treatment you find the moist successful for your garden pond, a consideration towards avoiding or lessening those environmental factors that are thought to be ideal conditions for blanket weed growth, will go a long way to sustaining a healthy pond, clear of the dreaded algae!