The CuLator Metal Eliminator and Stain Preventer Ultra PowerPak 4.0 removes 4 ppm stain-causing metals from your pool and spa water, which prevents pool staining and water discoloration. Treats 20,000 gallons. Simply place one CuLator Ultra 4.0 into your pump basket for one month or longer depending on your metal level. The CuLator Ultra 4.0 will removes and traps dissolved metals and can be used seasonally. The CuLator Ultra 4.0 removes rust, iron, copper, manganese, cobalt, nickel, silver, aluminum and even lead from your fresh or saltwater pool. CuLator is non-toxic, easy to use, and is phosphate free, and made in the USA.