So I did one treatment of stain free with metal free, and it worked great. I then brought up, and maintained chlorine with small doses of cal hypo through the skimmer. A week later, and I notice the stain reappearing. It is not nearly as bad as before, but I notice it. I was thinking that maybe it is the result of the metal free breaking down and releasing the metals that had not been filtered out yet. I'm probably wrong though. I plan on purchasing the KemTek HEDP and 4ppm CuLator that you recommend to try. The KemTek says it "prevents" stains, while the CuLator catches metals out of the water. I'm wondering if I should first use the Stain Free to get the metal stains off my liner, and back into the water for the CuLator to catch. Or will one of those products remove the staining on my liner instantly like the stain free did? Thanks.