Another Copper Treatment Question! Adding new fish to QT already under treatment?

[mandyplo]

So I was under the impression that the reason you slowly bring the copper concentration in your tank up to 0.5g/L, in 2 doses over 48 hours is to slowly acclimate your fish to the poison.

Others are telling me you can add new fish to your quarantine tank which is already at 0.5g/L of copper at any time.

My assumption was that I would have to finish this 4 week copper treatment on my current 3 fish, and when I transfer them back to my display tank I could remove the copper from the water with carbon filtration, and start a new treatment with new fish from square 1.

Do I have to start at square 1 with new fish? Or can I add new fish to my QT tank which is already at 0.5g/L copper, and leave that new fish in there for 4 weeks, even if my other fish are already 2 weeks into their treatment...

Thanks hoping someone can provide clarification.