I have the same understanding as you. Having been through the AA stain removal treatment before, I don't want to do it again.

If it's not the salt that's adding metals to my pool, then it has to be our city water (despite the post from Sean {no offense Sean })I still suspect the salt/SWCG system since it's only an issue when running the SWCG). There's no equipment or anything else that I put in the pool that would be adding metals (thanks to the methods taught here, there's not much I have to add to the pool ). And since city water is the only source of water I have to top off the pool when we don't get enough rain for awhile (not often), I'm stuck dealing with it.

It's been reported here that Jack's Magic Pink Stuff is more concentrated than the Purple Stuff I've been using, so I may give that a try so I can use smaller doses/use less. However, I'd still like to know what is it about the Purple Stuff that makes it more suitable for salt pools, or is it just marketing BS?

PS - I find it interesting that a couple of coworkers of mine who use the same SWCG system (one has a vinyl liner IG pool, the other a fiberglass IG pool; we are all on the same city water system) have the same issue I have.