Interesting. I didn't eat there (Yeah, it says I'm from CA, but my mom lives in Nashville), but we went through the place, and checked out the tank. I didn't see lots of disease, but I did see lots of fake corals. However, what are you going to do with that kind of display? Of course they're fake corals.
Right across the corridor, on the other side of the mall was a ray touch/feed place. They had a few random tanks around the edges of the place, but the main show was the ray feeding. $1 bought about a half dozen sardines, or something, and they show you how to hold them so the rays can get them out of your hand without giving you a hicky.
Anyway... I remember in the restaurant, the "main" tank was ceiling to just below floor, IIRC, and probably about 20 feet by 10 feet. The water had lots of debris in it.