Your thought's on re-stocking my 90g...

I would say that a 230 gallon tank is the smallest tank an emperor should be housed in, and it will grow out of that eventually.
They act completely different in a large aquarium, in a small tank they seem shy, in a big tank you can rush the glass and they come right up to you to see what your doing.... they are too shy even in a 230 if IMHO