I thought it was fantastic. We got a tankside table, and there were starfish, other fish, but the highlight was this massive 3 ft grouper which swam right along our edge of the tank and completely distracted us out of conversation!
I would recommend doing lunch, and getting there early. We actually misread our reservation as 11:00 when it was 11:30, when the restaurant opened, and so when we got there 15 minutes early we were 45 minutes before the restaurant even opened!
But we were the first people in the restaurant so we asked the hostess if we could have a tankside table. So if you have your heart set on that, I would say get the earliest lunch ressie possible and then being there early. I think there are only 4-6 tank tables in the whole place. If there is nobody else in the restaurant when you get there, your odds are better than just showing up for dinner or some other time when there may or may not be a table, or other people may be waiting for them. Also lunch is cheaper.
Food was outstanding, we had a charming server named Alejandro who was perfect and professional in recommending what was freshest, best, and some of the stuff he said was better weren't the really *emphasized* dishes on the menus, so it was great to have that. We ended up spending almost two hours and all had appetizer, dish, and dessert... but I'm sure you can get out quicker than that - we were just having too much fun!