I use Bar Keeper's Friend. The primary ingredient is oxalic acid, which IMO
is the next step above vinegar. It does wonders on hard water stains on aquarium glass as well as my pots & pans. I rinse it real good afterwards. But it's not a harsh acid and I don't do anything special to make sure it's removed. In fact, I don't even wear gloves when cleaning. I don't have to use elbow grease unless it's crusty / thick layer.