I always see different, and often imo better group dynamic when I move fish around and change up their tank mates. I've had the same group of pbass not be very food aggressive, then one day out of no where, or because of the addition of new fish they become violent eaters.
My 450g has 4 pbass, 3 gars, 2 silver aros and a tsn. Those are really the only fish that come meet me for food. They used to all be fairly calm. They'd ocassionally splash out half a gallon of water or so... but the last two times, I got drenched.. easily 5 gallons.
So as far as your question goes, I wouldn't know specifically, but you don't necessarily need a big group or anything in particular for character to change.
