Me too Dave! I love the fiberglass, stains and all. I noticed the same thing - my stains always seem to appear in the same places. My opinion is to put the sequestering agent in first, so whatever metals are still in solution will be filtered out. Then again when you do a stain treatment, so that the metals will bind to the sequestering agent as soon as they go into solution. My plan this year when I open is to put in the sequestering agent, slowly raise my chlorine, and balance the pool. I plan to run low cya (about40) so that I don't have to keep my chlorine very high. I also plan to keep my ph around no higher than 7.4. What I think, and it is only what I think so far, is that when the ph is low, the chlorine is more potent, which can let any metal in the water fall out onto the surface of the pool when the filter is off and the water isn't moving. But on the other hand low ph keeps the pool on the acidic side, which keeps the stains in solution, making the sequestering agent able to get rid of the stains before they fall onto the surface of the pool. This is why it is so confusing. So in my opinion lower ph with lower chlorine levels should keep the pool less suseptable to stains. I really don't know yet!! I am still in experimental stage - every time I think I know how and why the stain comes, something happens to destroy my theory. Anyway this is my plan for this year, I will let you know how it goes. I think keeping the filter running for 24/7 for the first couple of weeks after adding the sequestering agent is the most impotant thing when I first open the pool. I have never had stains when the pool is first opened, it seems it happens when I shock the pool on opening. That's why this year I plan to put in the sequestering agent first before taking the water up to shock levels. Keep me informed on what you learn too, maybe we can figure this out!