Blanket weed or string algae is one of the most prolific aquatic weeds known to pond keeper’s world wide. All these types of algae are not plants although some types do look similar to certain plants.
The growth is increased by bight sunlight, unshaded areas and shallow running water, especially over waterfalls, and can grow very quickly. Nutrients such as Nitrates and dissolved ammonia are produced by the over feeding of fish, these are a food source for algae and blanket weed.
Apart from the normal growth of photosynthesis, the blanket weed will grow even faster.
If it is left it can cause oxygen depletion and stress the larger fish causing obstruction.
You need to combat the weed by killing it off, if you just pull the weed out of the pond it releases more spores, this then produces even more weed and increase the problem.
Return from blanket weed to water quality