Why would the coral be stretched, obviously they would add more different types of coral maybe even some cool underwater ferns or plants. The same movement that is used in the fish could essential be used in some greenery that could sway back and forth.
If by "they", you mean Jim Sachs, the author, artist, graphic designer, and programmer of the Aquarium, he's going to add a 3D background similar to how you describe in the next year or so.