Mine has more peaceful fish, almost all are about 3in, but there doesn't seem to be one "boss," instead each fish seems to have individual fish they are boss over. It is very interesting.
Firemouth - boss over everyone, except blue acara
Blue acara - boss over everyone, except larger curviceps (!)
Rainbow cichlid - boss over everyone except the firemouth and acara
Large(er) Curviceps - boss over everyone except firemouth and rainbow
Smaller curviceps and Bolivian ram - bottom of pecking order, but do not hide or picked on unduly