AlgaeShield is treatment and prevention. It kills existing algae and defends your pool against algae for up to 30 days. Use AlgaeShield each month for a summer of clean, crystal clear water. Close your pool with AlgaeShield for an easier spring opening. UPC 061558901324 Item Form Liquid Brand Name Earth Science Laboratories Unit Count 32 Fluid Ounces Product Benefits Prevents Algae