Try bringing it up to around 50ppm. See how that does for you. You may end up wanting to take it even higher. One benefit of running a high CYA pool is that it actually allows you to test and add bleach less often. One of the other moderators who isn't active on the forum anymore lives in NW Louisiana. She deliberately runs her pool with a CYA of around 80ppm for that very reason. Otherwise she finds that she can't keep chlorine in the pool and is constantly adding it. As long as you maintain the proper chlorine levels to compensate for the higher CYA, you are fine. http://pool9.net/cl-cya/