HomeWhy do fish and other living things have different roles in the aquarium? What are the functions performed by algae?

What are the functions performed by algae?
      Algae are organisms that live in water. They can be single celled or many celled (sea weed). Algae provide food for the fish. For example some fish eat algae.
     Although it is important to have some algal growth in the aquarium, excessive algal growth can be unhealthy for an aquarium.

Why is excessive algal growth a problem?