If you medicate copper into your DT it is ruined FOREVER. Undisputable. Hyposalinity is the wise choice but you're going to kill lots of things in the DT by doing it there even so.
Strictly speaking, right now you need to use your new tank as Hospital Tank (
HT) and you need to put what's ill in the hospital, not the other way around. Then afterward (as long as you avoid copper treatment always), the tank can alternate between Hospital Tank & Quarantine Tank (
QT), use to PREVENT disease getting into your tank in the first place.I like to store my HT/QT dry between uses to eliminate any lingering issues as far as living organisms go.
Some good info on the difference
here. Although I don't agree with all of it, or rather issues they miss, it's pretty good.
Ian