That ring around your toilet or tub is a common problem with our water in this area. You may try some of the cleaners out on the market and find that they can not get that ring off. For all you porcelain or cast iron fixtures Val’s Plumbing sells a mesh that we call sand screen. Use this mesh screen with your cleaner, or use it by itself. Its a great solution to that common problem and its only about a dollar a foot.