CuLator Metal Eliminator and Stain Preventer, rapidly removes and eliminates copper, manganese, and iron, and lead from pool and spa water. CuLator is nontoxic and works in fresh and saltwater. Simply place a pre-measured flow-through PowerPak in the skimmer. As water passes over, metals are trapped inside. After use, toss the biodegradable PowerPak away! Great for opening your pool! Start the season off metal free!