I've have a purple tang in QT with copper treatment for the last 3 weeks. Generally the copper level is at .50 and it seems like one last spot just won't go away. I've treated for ick in the past and in almost every case the fish seem to clear up within a week or two and I'll QT them for 4 weeks total under normal cases. So the question is, has anyone ever see ick hang on past 3 or 4 weeks?