Hey, sorry for the late reply. I was having tank issues, as in my 20 gallon reef completely crashed, but that's another story for another post.
With the QT you will want him in there for 6 weeks at the least, be sure the ich is no longer visible. Keep the fish in QT till ich has not been visible for atleast 2-3 weeks. As was stated just above me, turning the temperature up will help speed up the life cycle of the ich.
Some people even use hypo-
salinity to help kill the ich infection, they do this by bringing down the salinity of the tank to 1.018
SG. Marine Ich has a hard time surviving at this level of salinity.