What is black algae?

What is black algae?
October 16, 2015 sdcpro

“Black Algae” (actually called blue-green algae) typically grows in cracks and crevices on pool surfaces. Black algae is normally found growing in shady areas of the pool, however it can be found in lighter areas as well. It is known for a heavy slime layer and is impervious to normal chlorine levels (1.0 – 2.5 ppm). Slight cracks in plaster or fiberglass walls are perfect breeding grounds for black algae especially when the pool is not properly maintained.