Prevents ugly stains, scaling and brown water due to minerals. Will actually lighten some stains! Restores brilliance and shine to your pool water. A must for areas with heavy iron content or well water. Helps maintain the appearance of your swimming pool and spa. Prevents water discoloration. Controls iron levels and the levels of other metals in your pool water. Convenient to use. Initial Dosage: 15 oz. per 10,000 gallons. Weekly Dosage: 5 oz. per 10,000 gallons. For existing stains use 30 oz. per 10,000 gallons. Apply directly over stain if possible.