I battled with cyano for the past 2-3 months, vacuumed constantly and added more flow near the sand, nothing seemed to work. Bit the bullet and dosed chemiclean, been free of it since, never came back. I understand your position though, I'd be really scared to do it if I had all those beautiful colonies. My tank is still pretty new and just has some frags in it, so I just rolled the dice and it worked.