With a CYA of 230, I wouldn't pay any attention to nitrates and phosphates. Your problem is as unsubtle as dump-truck--your CYA is way, Way, WAY too high and you must get it down. Ben's discussion of high CYA is for 100ppm, to 200ppm (a theoretical max) and you are beyond THAT!
Carl I didnt notice the CYA of 230.
Steve