Got one in from the solomon islands about two months ago. He was a baby--about 2-3 inches (ordered online). I acclimated him for 45 minutes to my tank water, then did a pH/Temp controlled freshwater dip with Paraguard for 30 minutes. He did great through all of that but he still got ich. Best would have been to QT him but I was not set up for that, unfortunately.
The Ich has been minimal, though. Just a light dusting from time to time, as well as some scratching against the rocks that I see from time to time.
He has continued to grow and eats very greedily, and has had no visible signs of ich for the past several days, even though one of the new fairy wrasses does.
What I do, since I cannot catch all the fish and let the tank lie fallow, is soak every meal in Garlic Extreme and Zoecon to try to keep the fish fat and healthy, and so far it seems to be working.
What I would do if I were to do it again would be to try to secure a specimen from someone else's tank, which had been healthy for a long time. And still I would QT it. Any fish that comes in from the wild, though, is going to come in with something, and it's much easier to catch it early and treat it in QT than wait and deal with it in your main tank...