How'd you cycle your QT
tank? Over what period of time? Trying to figure out how much nitrifying bacteria might have been created and its ability to prevent ammonia spikes from new fish. Not that I can do the figuring, but others at this site would be able to.
One fish tomorrow. What will it be, by the way?. And better yet, have you given good thought to what you ultimately want to be stocked with? Don't start with the yellow tang
What size is your main where the fish might be going?
I started with 3 blue/green chromis hoping they'd be tame enough for the big tank and do some schooling.
With first fish, watch your testing levels often and be prepared for water changes. Got a place for pre-mixed water to age with a small heater and circulation pump? I keep a 32g trash can w/about 15g made up - when I'm being good.