Product details:

Brand May Vary Effectively controls most types of algae. Copper sulfate kills algae on contact and is most effective when applied in water 60 or higher. It works by coming in direct contact with algae. Very easy to apply. For best results dissolve copper sulfate in water and spray it directly onto floating algae mats or on the water surface directly above submerged algae. Very economical. For algae control use 2.5 lb. to 4 lb. per acre-foot of water.