Here is a question we get quite a bit. When the pool walls or stairs have staining, you can use a product like StainFree to take the color off of the pool walls, and it is returning the iron into solution, (putting it back into your pool water).
Once you do this you then need to treat the water with a metal removing agent or something that will help sequester the iron so your filter can take it out of the pool, otherwise it will eventually re-deposit itself on your pool surface.
We have tried every metal remover on the market, and we keep coming back to FerriTabs as the absolute best product for use when you are trying to remove iron and you have a sand filter.
Another product you can use with FerriTabs (or can try if you don’t have a sand filter is SeaKlear Water Clarifier) it will help remove trace minerals from the pool.
Once you get rid of the stain, when you add more water to the pool that is high in iron content you can add 1-2 FerriTabs and it will help take the iron out before the stain has a chance to return.