All Natural Stain Eliminator: Natural Chemistry Stain Free Extra Strength is ideal for treating metal staining on all pool surfaces. This natural stain remover contains a blend of industrial strength ascorbic acid to quickly remove metal staining without adding phosphates to your water. Tough on Old Set-in Stains: The industrial strength ascorbic acid makes this stronger for use on more stubborn stains caused by metals. Compatibility: Extrs Strength Stain Free is compatible with all sanitizing systems. Stain Fighting: Use with Natural Chemistry Metal Free for the ultimate 1-2 combination for stain fighting. Tested and Proven Effective: Natural Chemistry products are known for delivering reliable results and making water care less complex. Natural Chemistry carries an extensive line of pool and spa solutions that match your unique needs. This Natural Chemistry extra strength stain free is an all natural stain remover. Recommended dose is 1-pound per 10,000-gallons of water. It can applied by following way that balance pool water and lower chlorine level to at least 1 ppm. Then add stain free as per dosage around the perimeter of the pool with the pump running. Brush pool thoroughly. After brushing, if stains are not completely removed add more strain free extra strength. Add a pulp based filter aid to your cartridge or sand filter. If you have a DE filter, make sure it is properly charged. Add metal free at a rate of 33.9-ounce per 20,000-gallons of water. Vacuum pool slowly and thoroughly. Use metal free as a weekly maintenance product to guarantee a stain free pool. Includes 12 stain free container per pack. Comes in 1-3/4-pounds container.