Pros rely on acid-based formulations to dissolve many common water-related bathroom stains, which is why you need Zep Commercial 32 oz. Mold and Mildew Stain Remover. This professional-grade mold stain remover offers an acidic solution that makes cleaning easier by breaking up rust, soap scum and other tough buildup on contact. It works great on a range of surfaces, including acrylic, ceramic tiles, porcelain, laminate and more.