What is Black Algae?
Despite its name, black algae isn't actually an algae at all—it's a type of cyanobacteria. It forms in dark, blue-green, or black clusters that typically look like pinheads or small coins stuck to your pool’s walls, floor, or steps. Unlike standard green algae that float freely, black algae features a thick, protective outer layer and microscopic roots that dig deep into porous pool surfaces such as plaster, concrete, and pebble tech.
Because of this deep root system, standard pool brushing and regular chlorine treatments often aren't enough to kill it. If the roots aren't completely destroyed, the black algae will keep growing back.
