Yeah, a jd is going to be too big for that tank. You could maybe get away with a firemouth or a rainbow. You could try honduran red points (one for sure, maybe a pair that get along with one another). Sajica would be similar to the hrp. Spinosisimus. All nice fish with personality. If you go to a 40g (36" versus 30") you can think about 2-3 small cichlids from the list above. I've got one with a rainbow, a spino, a runty hrp, and a runty electric blue dempsey (which is going to have to be moved out as it grows).