We use Clean Shower (Arm & Hammer). Just spray it around the top when you're finished with your shower and you very rarely have to do anything with it again. It will take some time, but if you spray the shower a couple of times a day, it will eventually clean it up. Had a rental with a fiberglass shower stall that I was sure that we would have to replace, but used this over a period of a week and a half and it looked like new.