I got one recently, I like it alot. It mainly hides but sometimes cruises round the tank.
It's more nocturnal, stops hiding when the lights go out.
Despite it's mouth shape it appears to be a bottom feeder. Ignores pellets and mealworms that are floating, but cruises around the bottom of the tank diagonally - gobbling things.
It's semi-aggressive. It doesn't start fights, but doesn't take any crap. It bit and chases both my oscar and friedrichsthali when they flared their gills at it.
It's an interesting fish, I've only had a CK before and i prefer the afer.
BTW the photos I've seen of this fish are brown, but mine is jet black with strange eyes.