When my friend gave me his 75 and 45 gallon fish tanks, he gave me two Jack Dempseys as well. The one was in really bad shape, and lasted about 2 weeks after the move. The one that remained went nocturnal on me. She always hid in the castle ornamentation in the tank, and would only come out at night. I finally trained her to come out when I was awake by only feeding her when I actually saw her.
This was kinda disappointing, because there is this HUGE fish tank in the middle of the room, and no fish in it, as she was always hiding.
I actually get to see her now.