Pool Algae: How to Prevent and Treat It

Algae thrives when chlorine drops below effective levels, circulation is poor, filtration is inadequate, or phosphate levels are high. Any combination of these creates ideal conditions for algae blooms.

The most common type. Green algae turns water cloudy green and clings to walls. Treatment: shock the pool to 30 ppm chlorine, brush all surfaces, run the filter 24/7, and backwash/clean the filter as pressure rises. Most green algae clears in 24-48 hours with aggressive treatment.

More resistant to chlorine than green algae. Appears as yellowish patches, usually in shaded areas. Treatment: requires higher shock levels, Yellow Out or similar specialty product, and thorough brushing. May require multiple treatments.

The most difficult to eliminate. Black algae has a protective outer layer and roots into plaster and grout. Treatment: aggressive brushing with a stainless steel brush (concrete pools only), concentrated chlorine application directly to spots, and specialty algaecide. Often requires professional treatment.