Undesirable vegetation is a ponds primary source of algae problems.
This vegetation may be sub-merged growth (below the surface), emergent (growing from the bottom & visible on the surface) or surface (floating). Different control strategies are required for each instance. Quite often floating plants such as duckweed and watermeal are misdiagnosed as algae problems. In all cases, proper identification of your vegetation is crucial for a successful control program.