String Algae
String algae, otherwise known as blanket weed, looks like a lot of
filaments hanging onto rocks and any rough surface.
It can double its weight in a day, can become partially detached, float to the surface and can spoil your pond's look and feel. This type of algae has a tensel strength when pulled away from rock, making this task difficult.
Unfortunately, where you have a pond that you can enjoy, you will have a problem. The conditions that lead to algae are mainly warm temperatures, sunlight, nutrition in the form of plants and leaves that decay in the pond, over feeding your fish and, if you have too many fish, the fish waste itself can lead to algae growth.
This type of algae loves waterfalls and shallow water. High ph value is another promoter of algae.