Pool Stain Treat has the strength to remove stains from any kind of swimming pool. Simply add one bottle (2 lbs.) of Pool Stain Treat per 20,000 gallons to your pool in the affected area and watch the stains disappear. Pool Stain Treat continues to work for up to sixty days keeping metals water-soluble and preventing future stains. Pool Stain Treat is the most trusted stain remover in the Pool Industry because of its ability to remove the toughest pool stains. (Robert's Pools recommends this product for spot treating stains)