Leisure Time Metal Gon is an easy to apply, concentrated formula that prevents iron and other metals from building up in your spa. Use with each refill to quickly neutralize metals in your spa and prevent unsightly stains. This product reacts with any metal contaminant before it has a chance to form the unsightly stains. You only have to apply this product once per fill (of the spa). Metal Gon is compatible with chlorine, bromine, and biguanide sanitizers.