How to remove toilet bowl ring?

I have this problem too and it always comes back. I also have well water. The one thing that works for a few weeks is scrubbing with a pumice stone. I just put on old rubber gloves and scrub. You can order a larger size one on amazon.

Baking soda,viniger and dawn in spay bottle spray and scrub once a day. And ALWAYS,ALWAYS flush the toilet after use

Mr. Clean Magic Eraser and elbow grease have worked for me.

Snobowl Cleaner, Let it sit for few minutes with lid shut. you may want to open window. If it doesn't work the first time don't give up, keep using it about 2 or 3 more times it should be gone before you know it. Another alternative of Snobowl is The Works.