Tub/shower resistent to iron deposits
We have well water with lots of iron despite having a sand filter. It doesn't make our water look rusty or even have bad taste, but it takes a toll on our tub, toilet, dishwasher, etc. For the toilet I finally found a cleaner to take care of it, but our fiberglass tub is bad. I think that I used too harsh of a cleaner in my experiments of trying to get the stains off and thus damaged the finish which has made the stains come back quicker (after cleaning) than before.
We are now thinking of replacing the tub and are wondering if we should go with another material. Is there another material besides fiberglass that resists iron deposits or at least is more substantial when cleaning?
I read that tile was not good. Not because of the tile, but because of the grout which is really difficult to get iron out of.
What about cast iron? I worry about the finish again.
Are there other materials?