Most people in this forum will probably say leave the fish in QT
and monitor for 4 weeks. If the fish show no sign of parasite or illness, then it is safe to go in the main. After all why would you want to put the fish through more stress with medication? This is what I am doing now.
However, I have in the past used Seachem's ParaGuard as a preventive measure. I believe this contains a mild malachite green, so not too stressful on the fish. And I have not noticed any more stress than without. But I also do not know how effective it was, since the fish did not show any signs of illness.