quarantine corals?

[0sprey]

I don't bother with QT'ing corals or other inverts. I DO know someone who lost of bunch of corals due to a batch of nudibranch eggs on a new addition, though. The only other thing I'd worry about is the possibility of being forced to apply treatment in your main tank, if your original two fish become ill. Most treatments aren't invert safe and can be absorbed by the rockwork (making the system permanently unsafe for inverts). Taking the risk is your call. You'll want to be super-careful when you select your livestock, that's for sure. CB would probably be the way to go, in this case.