Ideally you would have some filter media for the QT
sitting in the main tank for about a week to get the bio-filter going. If that's not possible, then use new media and keep on top of your water changes. Check your water parameters 2x day for the first few days - week and keep plenty of pre-mixed change water on hand. If you are using copper (cupramine/seacure), medicate the change water to the correct level before adding it to the QT
tank. Yes, you will want to use carbon at the end to help remove it but copper traces will probably always be in the tank.
Make sure you have a Seachem copper test kit on hand to monitor your copper levels.
I've been lucky enough to catch the outbreak early enough to treat it with hyposalinity. As I had to remove most fo
the rock to catch the fish and set up a new larger QT
, I was also able to get my filter going first.