My swimming pool is 31,000 gallons. The thought of filling that with fish - so it looks like a tank and not a few random fish - we are talking about SO MANY FISH!
For me it would seem like rare fish would be lost in a 30,000 gallon tank. i'd save those for smaller tanks. If I recall reading about Copps' big tank, he's adding huge numbers of more common fish - anthias, tangs, etc. Adding a $1,000 fish that you might never see....but then again, if you can afford a 30,000 tank, stock the whole thing with rarities.
I'm just blown away by this tank. The fact that it's the same size as my swimming pool is just amazing to me.