Professor Amos FAST Toilet and Tank Cleaner Duo with Microbial Maintenance Make your bathroom shine and sparkle. Clean and deodorize with this powerful toilet and tank cleaner. Its thick, concentrated formula helps dissolve lime scale, rust, hard water residue, mold and mildew stains. It's ideal to use in showers, sinks and tubs. You also get Professor Amos's FAST Microbial Maintenance to keep toilet pipes odor free and clean flowing.