Clown triggers can get quite mean as they get bigger and settle in the new tank. They are known to pick on lions.and will actually kill them...as with any other fish they decide to take a hit on.
The Emperor may require a larger tank as it gets bigger as a 125 is about the smallest to house an adult. They also require plenty of live rock in the tank to graze on and hide. You should wait about 6 months at least before adding the Emperor...this will alllow the tank to mature. They do better in mature systems.
Green Birds are jumpers...make sure your tank is covered.
Powder Blues are a littke spooky...but once they settle in they too can be mean boggers.
You can have about 1" of fish per 5 gallons of water. No hard fast rule as some fish such as triggers are big poopers. So, you can have about 20" of fish give or take a little.
Others will tell you that you can exceed the one inch per 5 gallons based on filtration. I beleive that to be risky and not worth the possibilty of total loss due to a power outage and/or equipment failure.
In my opinion, the fish you have on your list will exceed the one inch per gallon rule once they reach adulthood. I would not add another fish to that list.
I've been in the bobby for 30 plus years and do not consider myself to be an expert. The above is JMO...for what it's worth...
