CrystalClear, 20 LB, Algae Off Ag Pro, Granular Algaecide, Algae, Off Works On Contact, Removing String Algae Quickly & Efficiently, Applications Are In Square Feet Because Of It Being In Dry Form, Once The Product Is Applied, It Will Fall Through The Water Column, Does Not Dilute, To Make Contact With Algae, Bucket, Light Growth, 3Cups/1000SQFT, Heavy Growth: 6Cups/1000SQFT, Gallon Treatment = 400,000 Gallons, EPA Registered.