Interesting to see they still have this species. It used to be that they were in underground aquariums that are now part of the Manta queue and aquariums.
That is where the guide said they came from. Presumably no other facility had the room to keep them. They are kept in an interestingly netted enclosure- obviously to keep them from jumping out of the tank. This was the only portion that was glassed over and the only portion that wasn't shaded. There was also a great graphic explaining the double-jaw system of morays.
It is very likely we'll be seeing a new eel exhibit in the near future,though. SeaWorld (or RideWorld) is building another new rollercoaster called the Electric Eel, which would include an aquarium. It's set to open next year I believe.