Your regular daily cleaner might not remove these materials. Acids can cause harm very quickly, so always protect yourself with gloves and goggles. Pour the acid cleaner from low down so it won't splash. Use your scrub brush carefully to avoid splash as well. Flush the toilet twice to remove excess cleaner when you are done.
Acids corrode metal.
Use acid cleaners only on porcelain toilet bowls. Don't mix acids with bleach. This creates chlorine gas that can kill you. Janitorial Products Pollution Prevention Project - Sponsored by US EPA, State of California, Santa Clara County, the City of Richmond, and local government agencies. Written by Thomas Barron, Carol Berg, and Linda Bookman.