guppymonkey
Fish Herder
With a lot of small tetras (which seems to be the sort of fish that you are currently stocked with) you are limited with the types of large fish that you can add. Even if the larger fish aren't very aggressive they will eventually either kill, eat or harass the small fish to death. Even relatively non-aggressive fish such as Severums and Silver Dollars will bite other fish, especially smaller fish. If you want to add larger fish you should either find new homes for your small fish or live with the good chance of losing many of those smaller fish.