For years I have tried desperately to remove the hard water deposits on my toilets. It was made worse because the previous owners used those toilet cleaners that turn the water blue. My toilets were striped with this blue ink. No matter how hard I scrubbed, I couldn't get the stain off.
One day I found a product called Pumie Scouring Stick. It is the BEST tool I have ever used for removing stains, mineral deposits, rust and algae deposits on porcelain, concrete, masonry and iron. It removed that blue stain with so little effort, I couldn't believe it.
If you want to get your toilets sparkling clean, I highly recommend this product. It's nothing more than 100% pumice so it's completely safe and nontoxic.