Lawrosa, I have been trying to figure out how to test for, remove, control, or live with stains for about 11 years now. My conclusion is that every time I think I have it figured out, something else happens to make me wonder if the "stain gods" are just having a little more fun! What I really tried to do is figure out where the metals are really coming from. My well water does not show iron, but Jack's magic test showed the stains were iron. I do have a heater, so maybe they come from that. I just don't know. I also have three other friends that have the same pool, within different water sources and they all get stains too, so I have experimented with theirs too. The conclusion I came to is that I don't worry about where or how they get there anymore. Now I just get rid of them as they come, because no matter I still hate them with a vengence! My husband calls me "the stain nazi" You will figure out how to work your own pool water to keep your pool stain free. So, don't drive yourself crazy, but if you do please share your results with us, I love to learn about all the ways to get rid of stains, I add them to my "bag of tricks".