Reading this thread, I'll provide some of my input since there seems to be some misinformation.
It should probably be noted that this is in downtown Disney, which is totally different from the Disney parks. TREX is owned by Landry's, which owns a bunch of other restaurants, including Rainforest Café. Even though downtown Disney is technically Disney property, any decisions about the tank is falls back on Landry's; It has nothing to do with Disney!
I've been to Rainforest Café once before & it just ain't my thing. I only went for a rehearsal dinner. All you hear a bunch of monkey/ape sounds that are very distracting. Yes, it's always nice to see fish tanks but I hate seeing FO, & more specifically the fake coral inserts. I don't believe the fish at these restaurants are as healthy as they could be either.
On a side note, if you've been to Epcot, they've got a few saltwater tanks including an SPS cylinder, & seahorse tank/cuttlefish tank (not counting their big tank tons of fish/sharks). Discount some of the majanos in some of the tanks, it appears to be taken care of very nicely. The fish are certainly very health too. Being a passholder, I go every few months.