Quote Originally Posted by SoCalBoo
Posted below, but no one responded. If anyone can just respond briefly, I'd appreciate it.

Have 22,5k gallon IG, plaster, SWG. Have mustard bloom. Raised ch to 15 for a few days, it left briefly but came back.
You stated in a later post that your CYA tested at 60 ppm. If that is the case it is entirely possible that you did not get your FC levels up high enough. Ben's best guess CYA chart recommends 20 ppm
http://www.poolforum.com/pf2/showthread.php?t=365

I would give it one more try with chlorine and this time make sure you are at or above 20 ppm!