based on my experience, when they are the only fish in the tank, they will not school. in fact, they will find their own little spots in the tank. but, when you add other fish, and like nykademus said, and "predators" are introduced they will stick together. but, i'm telling you...those suckers get big and it is nearly impossbile to get them out later. so, if you dont' think you want them in the long haul, i'd pass.