Let me start by saying: I clean our toilet bowl every week! In the above picture it doesn't appear that way:( We have hard water and even though I clean every week I continue to have this STUBBORN toilet ring in my toilet bowl. Granted, we don't use our guest bathroom toilet as frequently so the water probably sits still for longer than our other toilet - but still, it is embarrassing to have guests come to use our toilet and then it look like I haven't cleaned in a month or two. I have tried everything to get rid of this stubborn ring. First, I tried using my trusted white distilled vinegar. Vinegar is usually great at getting rid of hard water stains ... but not a toilet ring like this. I also tried using bleach, to no avail. Then finally I read somewhere that you can use a pumice stone. A pumice stone? Really? I wasn't sure it would work and was a little worried it would scratch the porcelain. But for $1 I thought I would give it a try. AND IT WORKED!!!!! Why have I used so much time trying to clean the ring and within minutes for just $1 it had disappeared. AMAZING.
As mentioned all you need is a pumice stone.
After cleaning the toilet bowl (I prefer to start with a clean slate) get the pumice stone wet and start rubbing it against the toilet ring. And it will start disappearing before your eyes.
This is such an easy and natural solution. It takes no time and no chemicals are used.