What is blanket weed? How can I keep it under control?

There are actually a number of types of blanket weed,What is blanket weed? How can I keep it under control? Articles otherwise known as string algae. These different sorts all look and behave almost identically. The most common kinds are Cladophora, Oedogonium and Spirogyra. The word ‘Cladophora’ means branched plant and it is easy to see why this term is used when the weed is viewed under a microscope. The branch like formation is very easily seen.

It comes as a surprise to people to know that blanket weed is actually quite beneficial to a pond. It actively absorbs nutrients and minerals from pond water much like a vegetable filter would do. The issue with blanket weed is that it doesn’t necessarily know its own place; and when to stop growing!


There are three main factors that provide the perfect environment in which blanket weed will thrive. The first of these is clear sunlit water. The sunlight is required to fuel the photosynthesis process. Blanket weed also requires lots of nutrients; it easily absorbs nitrates and phosphates as it develops. These can be gained from tap water and also through fish metabolism. The final element that the algae needs is heat. A warm climate will considerably accelerate blanket weed growth, especially in shallower areas of water such as waterfalls along a ponds edge. Blanket weed will in fact stop growing throughout the winter, but will soon thrive again in the spring as temperatures recover.