I am understanding that there is a working relationship between CYA and FC....the higher the CYA, the more FC you need....but in any case, I thought that pools with FC above 4 FC were not safe to swim in? So, isn't one required to lower the CYA to keep the FC requirement around the ideal 2.0 ppm and the pool swimmable? My CYA is about 60, and my FC is over 5, so I'm replacing some water, trying to bring everything down...is this proper thinking? I did have some kind of algae in my pool, shocked it like mad, and my FC and TC are the same, so I think I've divided and conquered...once I get my CYA to about 40, I am switching over to bleach....