Does this apply to Indonesian Dats too? The sticky says they get up to 18 inches rarely in an aquarium.
As I've said, 2' would be ok for most Dats for quite a while. When (and if) you were able to get them to full adult size, I personally would be looking to get a bigger tank. The Indo pic I posted above is easily 20" and while others might be ok with it I personally would not want to keep it in a 24" wide tank.