Quote Originally Posted by mbar
The best way to test if they are metal or organic, is to crush up a couple of vitamin C tablets, put them in a sock, and rub them on the stain - if they go away, it is metal. You could also use ph down and do the same. If they don't go away with either of these methods, then I would try the same thing with a crushed up triclor tablet, rub it on the stain, or hold it on the stain. If they lighten then they may be organic. There is also a stain test by "Jack's Magic" that can help you tell what kind of stain it is. You can also try a stain stick that is sort of like a rubber coated pumice. To take the rust off your metal, I would suggest using sand paper. I don't know how or why it rusted - but sand paper should take it off. You can put a dose of metal sequestering agent in the water to bond with any metal that is in suspension. Your chemistry looks perfect to me now. However the stains could have formed some time that you had high chlorine levels along with high ph levels, this will let any metal that is in the water fall out and stain the surface of the pool. The sequestering agent hold the metals in suspension, so they do not cause stain on the pool. I am checking out a product that is supposed to react with the metals and turn them into crystals, therefore allowing the metal to be filtered out, instead of just staying in solution. It is by Proteam, and is "Metal Magic". Feel free to ask any other questions you may have.
Thanks for the fantastic advice. In fact, on the advice of my friend in the industry, I did rub/crush a trichlor tablet onto one of these stains and had the trichlor tablet rest on the stain for a time to see if it would fade, which it did not. So that implies that it is a metal stain and not organic (i.e. not algae) which is good in some sense. I'll double check this with the crushed vitamin C tablets in a sock, as you suggest. I may have to get my scuba gear out as most of these stains are at the bottom of the pool in the deep end. Seriously, I think there's a stain I can find that is more easily accessible.

Would it be worth my having my pool water checked for metals? If there is a continued source of rust shouldn't that be detectable in such a water test?

Thanks,
Richard