I used the manual filtration method for removing iron from my pool. However, now I have stains around water line. My water is still light green, and came to the conclusion that between the blue liner and yellowing from iron while filtering it is making the water appear green. When I fill a glass with water it is crystal clear. My question is if I can use like a half cup of iron out through my skimmer to circulate through pool then brush to get stains off? I have a pool that is almost 15,000 gallons so a half cup should not affect the water, right?