Oh, wow. Ok, that makes sense. Guess I'll be going to buy a metal test kit.

I don't really trust my pool store completely, either. Although, I do not go to a national chain store (whose name I won't mention) that seems to be run by uneducated teenagers -- we do have one nearby, but I won't go there!
My store is a family-owned business that has been around for about 20 years and the owners (mid-50's couple) do all the testing themselves. But I still don't trust them implicitly because they are running a business and they profit from my *needing* more chemicals. That's why I joined this forum.

I think you have a excellent point & I will get that water tested right away!
BTW, it's now been nearly 36 hours with the Metal Out and there is NO change in the stain. DEFINITELY the wrong course of action...
Thanks!