How do you get brown stains off the wall of a fiberglass pool?

I have a fiberglass pool and I am constantly battling with iron stains. It is not impossible to remove the stains. I get brown stains in my pool and I treat them with jacks magic stain solution #1. Check out their website. They show different pictures of different types of stains. The stuff does remove the stains quickly, but it is expensive. Hope this helps.