People have different experience with ICH, i have had minor outbreaks in well maintained understocked tanks where all of the fish (including a powder blue who was the offender) recovered fully from it. I have had moderately stocked tanks where one or two fish died and the rest recovered. I have never seen a heavily stocked tank survive an outbreak.
This experience leads me to believe that defeating ich is as much or more about keeping your stock light to moderate than it is about quarantine procedure.
Of course, it depends on the health of the fish in general in your system also. If they are all stressed, if its a pretty new tank or if you got them all at once, they wont tolerate it as much even lightly to moderatly stocked as they would if they are acclimated in a healthy mature tank (again, just my experience).
I am however, setting up a QT tank ONLY because i may want to try an ich prone powder blue (hadnt decided yet) and since he would likely be the last one going into an already stocked tank....he will def need to be qt'd.
However, if i end up not getting such a fish...im not sure ill quarantine any. Ill chose hearty fish, add them slowly and stop when the tank is moderatly stocked.
Not saying thats what you should do....your mileadge may vary.
