Not really, there are some crazy aggressive african species, but you can overcrowd a 75gal aquarium with 12-18 6" fish. To do the same aggression spreading for the big CA cichlids, you'd need a 240g or larger (much larger in some cases), but it can be done. There are plenty of videos of people with monster tanks with pretty high numbers of large & aggressive cichlids. It's just not possible for most people to have the space or the money to own such a tank.