Changing Tanks

[Stormy]

Hello all, I have a 125 gallon planted tank with 6 juvies around 3", 4 Cobalt blues and 2 Red turks. After a bit of a rough start, things are going well. I got a chance to pick up 8 discus for a great price, 2 of these Discus were once Barb Newells. I got these Discus today. I have a planted, cycled 75 gallon tank that I was preparing for more Discus, so the timing was perfect. I under estimated the size of the 8 Discus. They are 3 year old adults, these are big beautiful fish, to big to put 8 in a 75 gallon tank. They make the tank look small. For now I'm going to use the 75 as a QT tank for the adults but eventually want to move the juvies from the 125 to the 75 and the adults from the 75 to the 125. I don't want to mix these fish. My question is this.
How long should I wait to put the adults into the 125 after I take the juvies out to avoid any chance of them getting sick from any infections or parasites in the water from the juvies? Can I just do a ton of water changes for a couple of weeks on the 125 once the juvies are out or would a weeks worth be good?
I have 2 cycled 20 gallon QT tanks I can put the juvies in while I wait. Once the adults are in the 125 I'll move the juvies to the 75 and repeat the process so the juvies don't catch anything from the adults. Any help or suggestions would be most apreciated, thanks in advance.

[Stormy]

The lack of responses tells me I'm making an issue where there really isn't one. You guys are just to polite to tell me.:)

[Tropical Haven]

If your 125 gallon tank has any infections in it water changes will do nothing to get rid of it. In order for your 125 gallon to be safe if it is infected then you would need to either treat it for the infection or drain it all out and sterilize the tank and all the filter media and start the tank over from scratch.

[Stormy]

Thanks for the advice, most appreciated.