BioSafe Systems 3015-50 GreenClean Granular Algaecide, 50 lb. Treats up to 100,000 gallons Non-harmful to fish and aquatic plants when used as directed Alternative to harsh chemicals  Chlorine, copper and phosphate-free Begins working on contact, killing algae fast; results in 24 to 48 hours Immediately begins fighting algae blooms, releasing vital oxygen into the water body as it biodegrades