different types of algae
Resistant algae may be one of two types: Lyngbya or pithophora. Lyngbya algae species form green, black or gray clumps made up of thousands of cells that may be found on the bottom of the pond or floating along the surface. Pithophora is a dark green filamentous algae often referred to as horsehair algae.
Planktonic algae float in the top layer of your pond's water. They are made up of tiny plants that make the water appear pale green to brown. The presence of this algae can cause an unpleasant odor in your pond. Planktonic algae can deplete your pond water of oxygen.