How do I clean algae from a pool?

Scrub with a stiff-bristle pool brush first to dislodge algae clinging to rough surfaces, then shock the pool with chlorine (or non-chlorine shock to swim sooner). For stubborn mold or black algae, use a pumice stone on plaster after testing a spot. Skip expensive spot removers—brush and chlorine work just as well with elbow grease.