I don't know if you got over to Caesar's or not but they have a tank that is about the same size as the one at the Mirage. The only thing thats different is that they conduct tours in the basement of the whole operation.
I was out there in Jan. and got a personal tour of the basement. The day my wife and I were there the sign for the times for the tours was not there, so I asked a worker if they were going to have tours that day, so he called the aquarist in the basement. They told him that they were not because the elevator was on the fritz. But if it was just the two of us we could take the stairs. HeckYeah! so the guy came up and got us and we stayed down in the operation rooms for an hour and a half, WOW!
Needless to say it was the highlight of my trip! The head aquarist escorted us back up to the main lobby when we were done and gave me his card. He told me to call him any time if I had any questions. I have called and he's given me some advise.
The best part of it was seeing their personal tanks and experiments behind the seens. I'll never forget that trip.