Using bleach on a toilet bowl ring may seem like a good idea, but it doesn't do the job. You should try to catch rings early, as they will be much easier to remove and may even come off through a good cleaning with an acid bowl cleaner. If the bowl cleaner doesn't get rid of the ring, you can try using a green, nylon-backed scrub sponge along with the acid. If you have an old ring, you'll have the best luck using a pumice stone. Take the stone and wet it with the water in the bowl, and then rub it on the ring. Make sure to keep the stone wet the entire time you're scrubbing. Pumice stones should only be used on vitreous china toilets - never on colored, enamel or plastic fixtures. Once you've gotten rid of a ring, weekly cleanings should stop it from coming back.