Good ol black devil catfish. Probably one of the most aggressive fish you can own. Probably the only fish Ive seen not only kill every other fish with it, but kill the filter intake, output, the bubbler, and try to get the heater. Also tried to kill the siphon during any water change. I wouldnt even call them aggressive in normal terms as it doesnt do it to promote dominance or claim territory... they're just straight up mean and homicidal.