99% Copper Sulfate Pentahydrate. To be used for large bodies of water, not small decorative ponds, water features, or pools., Controls most species of algae like filamentous, string algae and swimmers itch. Copper Sulfate should be used as a pond algae treatment on actively growing algae in water temperature above 60F., Most effective when cast out on top of thick floating algae mats. Be aware of how much vegetation you are treating at one time. Eliminating too much at once can deplete the oxygen levels too quickly for your fish., Granular Copper Sulfate, 5 lbs, DO NOT use in bodies of water that include Koi, Goldfish, Trout, or Grass Carp. These types of fish are sensitive to copper sulfate products.