Well, as i understand it pleco's are not aggresive. But today i woke up, came down stairs and saw that my common pleco was chasing my arowana, jack dempsey, auratus, banded leperanuis and pretty much every other fish he saw. I have no clue why he wsa doing this, but i just wanted to post it and see if you guys have had the same thing happen or perhaps why he was doing this. Btw my pleco is a bit bigger than a foot long.