AlgaeShield 85471 1 gal Algaecide - 4 per Case for pool maintenance. The proprietary formula holds copper tightly in solution while allowing it to be completely accessible for killing algae. This makes Algaeshield highly effective. Rapid and complete dispersion is another unique feature. This allows the copper to get where it needs to be to kill algae, even if circulation is not optimal. You don’t have to worry about this algaecide settling to the bottom. Algaeshield gets under ladders and in all those places that are difficult to brush. Just 1 ounce per 1000 gallons of water applied every 30 days is all takes. It’s the only algaecide you will need.