Ctenopoma acutirostre is by far the most common species in the genus. They get about 6 inches, sometimes slightly more. They do fine with bichirs. I was thinking about setting my 75 up as an african oddball tank, with bichirs and ctenopomas mostly.
I don't think they are very picky.You already have it, right? pellets are the easiest thing to feed it, but pretty much anything frozen is fine. It will probably eat any live insect/worm/other invertebrate it can fit in its mouth. Crickets, earthworms, mealworms, flies, etc. Feeding them exclusively is a waste of time though.