Black Algaetrine concentrate controls the growth of problem black algae in swimming pools. The formula contains copper and special penetrating agents that kill and prevent regrowth of the most deeply rooted black algae cells. Is safe for all pool construction types and allows swimming immediately after treatment. Black Algaetrine works best when added by itself directly to pool water. It should not be mixed with soap or other cleaners, or pre-mixed with other water treating chemicals.