How many fish should I QT at one time?

[-Logzor]

I am planning a fairly large fish order, probably up to 8 fish, including anthias, midas blenny, six line wrasse, etc.

My QT tank is 30g tall. It has some rock and coral frags in it currently.

Is it safe to QT this many fish at once?

What should I keep around for treating the fish if they have parasite/disease? I have another tank that I can treat separately in.