In The Swim Black Pool Algaecide 1 qt.
Black algaecide is specially formulated to overcome black algae's resistance to other chemicals to help kill the algae and prevent future growth. Non-clouding and non-foaming. Active ingredient: copper.  Initial Dosage: 12 oz. per 10,000 gallons at the onset of black spots. Weekly Maintenance: 6 oz. per 10,000 gallons.  Particularly stubborn algae blooms may require multiple treatments.