AQUA DOC Advanced, Professional Grade Formula. Pool & Hot Tub Stain and Scale Control. MAXIMUM STRENGTH STAIN PREVENTER FOR HOT TUBS & POOLS AQUA DOC is your premier source for spa and hot tub cleaning and maintenance! They are committed to high quality, low prices, and the best service to their customers. They want everyone's experience to reflect a high commitment to these values. If you are looking for great products to help take care of your pool and spa, you have come to the right place! Stain & Scale Prevent provides protection to prevent calcium and hard silica scale build up. The best stain and scale controller for protections against all types- even metal stains. STAIN & SCALE CONTROL IS RECOMMENDED FOR: Spas and Hot Tub stain and scale prevention, Swimming Pool metal off and rust stain removal, Controlling hard water in spas and pools, Removing rust and lime stains, Stain and scale removal of pre-existing build-up, Professional and industrial