Backwards quarantine - has anyone ever done this? *

[HappyFace]

Instead of quarantining new fish, quarantine the old ones?

Instead of putting my new discus into the QT tank I'm thinking of moving the fish I have into the QT tank. I would sterilize my display tank and sump -run bleach water through it for 24 hours, scrub and wipe everything down with bleach water. After cycling the display tank, put the new discus in. Completely cover the tank since my room is so bright. Slowly uncover a little bit of the tank each day.

This way my new discus will be in a more spacious tank (200 gal versus 100 gal) and they won't have to go through a second, traumatic move from the QT tank to the display. The new discus will be worth more than my current lot. They will be hand-picked by me from pictures or video the seller sends me. If I end up having to cull my current fish the new fish will already be happily acclimated in the display tank.

Basically, I would be quarantining everyone and medicating both tanks of fish for diseases (one med at a time) to hopefully eradicate anything they might be carrying. I'm going to purchase one "cull" discus with the new ones then after 6 week quarantine is over, put the new cull discus into the QT tank with my old fish. If any fish die or get sick in 3 weeks then cull all of my current fish and sterilize the QT tank. If everyone does ok then in 3 weeks place the old fish into the display tank and pray.*