5 Things to Know About Black Algae in Your Pool

Brushing is your primary weapon Black algae has a waxy protective layer and roots into plaster or gunite. Chlorine alone cannot penetrate that barrier—physical brushing breaks it so sanitizer can work.

Keep chlorine levels consistently high Never let chlorine drop below 2-3 ppm. Weekly shocking during warm months is essential for prevention.

Use a stainless steel brush, not nylon Nylon brushes are ineffective against black algae. A stainless steel brush is required to scrub off the protective layer.

Spot-treat visible black spots directly Scrub hard, then apply a chlorine tablet or concentrated shock treatment directly to the spot. This targets the algae where it lives.

Prevention beats removal every time Once black algae takes hold, it is stubborn and difficult to remove. Regular brushing and consistent chlorine levels are the only reliable way to keep it from coming back.