HALT 50 ALGAECIDE ALGAE'S WORST ENEMY! Rely on concentrated Halt 50 Algaecide to kill and prevent all types of algae. A single quart of this super concentrated swimming pool algaecide treats up to 240,000 gallons a great value! Plus, this non-metallic, low-foaming formula will not stain or discolor hair. Swim immediately after treatment. Great for all pool types. Maintenance dosage: 1-1/3 oz. per 10,000 gallons. Buy 4 quarts and SAVE!