Good advice ^above^ and do similar, Prazi-Pro followed by hypo-salinity treatment SOP. Tangs or signs of any Ich then onto a full Cupramine (copper) treatment. There is fine line in using QT systems to weed out parasite possibilities as you don't want to overly stress new fish in a to small, to bright and busy without any hiding areas tank nor do you want to put them in a to large and to comfortable of accommodations in hope of seeing something that may be wrong. So without some type of treatment during this QT process it is not fully effective.
Cheers, Todd