How long to leave quarantine tank alone?

[Cal_stir]

daniella3d is correct, i've had several battles with ich in an established q tank that i use mainly to quaratine corals, made the mistake of quarantining a fish with some corals, the fish had ich, and now i quarantine my fish in a bare 5 gal hospital tank, the corals remained in the q tank for 45 days, no ich transfered to the display.