Blagdon Algaway Blanket weed is an effective treatment for ponds which helps to eliminate blanket weed (string algae / thread algae) altogether. Not only is it an effective treatment against Blanket Weed, but it also encourages plant growth along with being safe for wildlife and pets. Blanket weed can be a big problem for a lot of pond keepers as it quickly covers the pond and can easily damage filters by blocking/clogging them up, so it is best to stay on top of Blanket Weed when it starts to form on your pond. By using just one cap full of Blagdon Blanket weed for every 650 litres of water, you can effectively treat your pond. This large tub treats 45,845 litres (10,085 gallons).