ProTeam Severest Algae Treatment is used to treat outbreaks of blue-green, black, and mustard algae. This product contains 7% copper for extra algae killing power. It also has a highly chelated formula which prevents staining. Severest Algae Treatment is an economical treatment method for chlorine or bromine pools. This product will help keep pool water sparkling and algae-free. Best of all, Severest Algae Treatment is made right here in the USA to ensure the highest possible quality, allowing you to buy with confidence.