4 Steps to Kill Black Algae in a Pool

Scrub the algae with a stainless steel brush The stiff bristles break the waxy coating that protects black algae from chlorine. Normal brushing won’t work.

Rub a chlorine tablet directly on each spot Hold the tablet with a pole or gloved hand and press it onto the algae. The concentrated chlorine penetrates the roots.

Shock the pool to 10–15 ppm free chlorine A high dose kills what the direct treatment missed. Brush the entire pool every day for a week.

Repeat until the spots are gone Black algae comes back if you stop early. Keep scrubbing and shocking until the spots fade and stop returning.