We have very hard (well) water, and coupled with a leaky toilet several months back...I ended up with a "smear" of calcium build up from the offending trickle. I tried everything, CLR included, and what finally worked for me was this type of metal mesh that I picked up a Lowe's. It's specifically for scrubbing off the calcium/lime/iron deposits and it literally took me less than a minute to scrub the stain off! Now that the toilet is fixed, the stain has not returned. I also use these cleaning tablets that you put in your tank. I also get those at Lowe's in a gray bucket with a yellow lid. Each one works for 3 months, and they are great!