I haven't got one, but just doing a quick search on them, I found a few sites. The Black Lancer catfish (common name) grows to around 6" for a female, 7" for a male. They are a softer skinned catfish and easily scratched, so be careful of the decorations. They like tubes/cave areas. They live in slow flowing muddy rivers in the wild. About a 55 gallon tank would be a good size for them. They do have smaller mouths for a catfish, so you can have any fish that won't fit in those mouths. Probably not neons or other fish smaller than neons, but ok for black skirt tetras, phantom tetras, harlequin rasboras.
They do tend to eat after lights out more than during the day. Males have a whitish colored genital papilla that helps make them easy to sex.