A new blue powder tang that I purchased introduced ich into my reef DT. I moved him and most of the other fish to a large sump I'm using as a hospital tank to treat them with copper. There are a few other fish still living in the DT, as I have no more room in the hospital tank. How likely are the medicated fish to get reinfected with this same strain of ich once I put them back into the DT? At the moment I have no space to remove all the fish from the DT and running fallow for 72 days, but I understand immunity is temporary and not always guaranteed. What are my options?