Upside-down catfish = carnivorous??

I always thought upside-down catfish was the common name of Synodontis nigriventris

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?)
 
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