first off "and a pike, gar, or arapaima wouldn't either" gar and arapaima are pathetic, predatory and aggresion are different, my gar gets harassed by the koi he lives with... anyway, i keep alot of the fish that have been mentioned in my 7,500g heated pond. i can give a pretty good idea of how these guys behave in the wild. dovii, sit out in the open ( the same spot all day every day though) and chase away everything that gets close to it. doesnt chase beyond that, just gets w/e out of his spot. catfish simply roam around and eat w/e fits in their mouth, no aggresion, just hunger. same goes for peacock bass/arrowana/gar, 0% aggresion 100% hunger. no fish are truly "aggresive" just defensive... except those goddamn convicts. by far the fish with the highest body count in my pond is this big 7in mutant male convict, bastard killed 2 peacock bass, a red bay snook cichlid, my poor old midas,an arowana,and 3 oscars over the years. when people argue over the most aggressive cichlids, its all nonsense and guesswork, they are really all pretty similar , it just comes down to the individual.