I have my Tilex Mold and Mildew bottle right here (it is one of my all time favorite products).
It says will work on non porous surfaces...
Glazed ceramic tile, shower doors, plastic, chrome, fiberglass, glazed porcelain, and synthetic marble.
If this is the first time you will be using it, you should purchase 2 bottles. Open a window!~ It is very strong.. Spray it very liberally starting from the top areas and let it sit for about 5 minutes. Wipe and then rinse with water. Keep the bathroom door closed.
Then work move to the middle areas. Spray, leave for 5 minutes, come back and wipe. Then move to the bottom portion.... You can go back and spot clean the areas that did not get totally clean..
From then on you can just do this 2 or 3 times a week to keep it clean.. This is what we do out at the lake house.. It also has terrible hard water.. I thought we would need to replace our bathtub until I purchased this product about 12 years ago.. It was the only thing that had ever worked on our tub!