It's the common name of a number of Syndontis cats, but that is the most common one to use that common name. (I just realized that sentence makes little sense.) S. Nigriventris gets about 4-5 inches long and is generally pretty peaceful. Like any fish, they will still eat pretty much anything they can get in their mouths. (Aren't fish a little like 1 year olds that way?)
Well, even though this guy isn't officially an "upside-down catfish", he swims every which way and often patrols the surface of the water upside-down. Beautiful!!