GreenClean Granular Algaecide Tablets An EPA- registered, non-cooper algaecide that kills existing string algae on contact! Visible results in minutes. May be used in ornamental ponds and water gardens containing live fish and plants. Same as the granular form - but in a compressed form for easy application use. Slow release maintenance application. Non-harmful to fish, aquatic plants and pets. APPLICATION RATES BASED ON POND SIZE: 1 tablet treats 175 gallons 2 tablets treat 350 gallons 3 tablets treat 500 gallons 4 tablets treat 675 gallons 5 tablets treat 850 gallons 6 tablets treat 1000 gallons.