IMO, QT new fishes is the best approach to prevent Ich outbreak spread in Display tank..
you may try hertana & artemiss during QT help boost the natural immune system of the fish before transfer to Display tank...
http://www.microbelift.com/products/home-aquarium/reef-and-marine/herbtana-reef/
http://www.microbelift.com/products/home-aquarium/reef-and-marine/artemiss-reef/
Cheers..
CFOh