Yes,very mean. But the meanest fish I've ever owned ( And I've had a bunch) has to be a dorado , Salminus maxillosus . He and my Devil cat or Crystal eyed catfish as I've heard them called always fought. The dorado always won though . Bigger teeth I guess , not the attitude. My devil cat has his own cave system that it continuously digs under the rocks in the 180 Gallon tank it's in . It is really mean though , It attacks anything that goes any where near it's territory including me. It absolutely owns the 16" Polypterus e. endlicheri that it lives with. The devil cat is 10" + or - . It's one of my all time favorite catfish , I promise you that. 
