Metal ions are present in all pool water and when present in excess amounts they can adhere to the pool surface. This is how metal stains form. To remove metals, Metal Gone sequesters the metal ions from the pool water and chelates, or binds, them until they are safely filtered out so they cannot dissolve back into the pool water to stain. Metal Gone also aids in scale removal and prevention. Regular use prevents the deposit of new stains and will continue to reduce older metal stains.