Black Algaetrine is a unique, patented combination of algaecides specially formulated to control black algae and other resistant strains. Black Algaetrine Features: Attacks deeply rooted black algae. Safe for vinyl, plaster, colored and fiberglass pools. Black Algaetrine Applications: Dilute in a bucket with at least nine parts of water before applying. To remove black deposits: Brush areas vigorously with a stiff or special algae brush immediately prior to application. This will help break up the black algae colonies that have formed. Apply Black Algaetrine (12 oz. per 10,000 gallons). Brush again once each day for two days following applica...   Click here for More Info