The guy used to be a reefer, he made two tanks on each side of his corner desk and connects them with an above water line bridge, awesome use of physics, want to do this with 2 nano tanks in the kitchen one day! he has a few vids throughout the thread of fish using the bridge to travel between the tanks.
That would be a wonderful river tank. Although I'd much rather have 2 6 footers because I could then keep different biotopes. And as stated the 24" width is a bit limiting when you get to that size, since you have 12' to play with.