SpaGuard® Stain & Scale qt: Scale or calcium carbonate build-up can cause damage to your spa surface as well as your circulation system. BioGuard's newly reformulated Stain & Scale Control does a great job of preventing scale—more than four times better than the previous formula—by introducing powerful agents that bond to problem-causing calcium ions in your spa water. Stain & Scale Control will also tie up metals in your water—such as iron, copper and manganese—that can cause stains and discoloration. Even better, you can use Stain & Scale Control to treat existing scale and metal problems.