5 Things to Know About Black Algae in Your Pool

Black algae signals a dead spot in your pool It is caused by poor circulation and low chlorine, usually in shady corners or on rough plaster where water barely moves.

Black algae roots into surfaces Regular brushing with a nylon brush will not remove it. You need a stainless steel brush to break up the roots.

Kill it with aggressive shocking and daily brushing Brush hard, then double- or triple-shock the pool. Keep chlorine high for several days and brush every day until the algae turns gray or white.

Vacuum to waste after it dies Once the algae changes color, vacuum it out to waste and scrub again to remove any remaining roots.

Prevent it with better circulation Run your pump longer, especially in hot weather, and pay extra attention to shady spots where water stagnates.