Applied Biochemists Algaetrine effectively kills off any green and mustard-yellow algae using elemental copper, restoring your pool to its former beauty. Copper is just as effective as the harsh chemicals other brands frequently use, and will not clog your filter, cause foaming, or affect water clarity. It even allows swimming immediately after application! Best of all, Algaetrine is made by Applied Biochemists, a leader in bio-based pool chemicals, allowing you to buy with confidence.