All other species of lower jaws and Turkana senegals are with him now. For one I would put in a tank with at least 24 inch depth front to back. The reality with the big lower jaw bichirs is that they probably won't hit their max size in captivity.
Not surprising. They dont have a lake or stream to grow big in. Any pics of this fish before you sold it? I just bought one off Preditory fins, 6-7"...