I live in New England and have a lot of iron in my water and every time I take a shower I noticed the walls of my fiberglass shower keep getting orange. How do I get rid of the hard water stains on my shower walls?
I guess you need to first deal with the iron problem. Have you tried water softeners? Industrial water softeners can remove dissolved ferrous iron, further precipitated iron can be removed by filtration.
A good oxygenating bleach might help you with the stains. Make a strong paste and scrub it. Sometimes even a shower gel would work. Put gel on the surface and pat it to foam, leave it overnight. Next day rinse it off. I once heard my friend mention about one such cleaner, Easy Off Fume. No idea how good it is.
Bear in mind that never use abrasive cleaners like the scrubbing bubbles. The best method I would suggest is using a rubber squeegee. After each shower, wipe down the walls. Don't allow water build upon the walls. Soap scum forms when the water dries and thus take less than 30 seconds to wipe down the walls.
Some natural products include bubbles, kaboom, vinegar and baking soda.
In some cases, it could be rust(since you mentioned orange colour). Take a look at an article on possible reasons of orange water (http://www.advancedplumbing.ca/blog/general-category/possible-causes-of-...).
Try 50/50 mixture of white vinegar and water. Let it soak for awhile then wipe off. Don't use anything that could scratch the fiberglass.
If it's really fiberglass, not acrylic, I wonder if a marine supply store would have a nonabrasive, biodegradable boat cleaner (not one with wax; that would be too slippery) that would work. I've not tried this so let us know if you do.