The only problem I ever had was with my female ornate. The first male that she was raised with had to be removed for his own safety. She now lives with another male and there are no issues. The lapredei are also fine with her as are several synodontis cats and SA Parrot cichlids.
my ornate is very calm and actually lives with a ray happily and most bichirs mouthes are small so buy baby ornate your only regret will be they are not as active a senegal
^This^ a 180gal is minimum for an Ornate or a 6'x2' footprint there are smaller polys with equally desirable patterns though palmas complex for instance
Somewhat related to this discussion: What is the (usual) growth rate of Ornates?
I realize there are several parameters like number of water-changes, temperature, food, feeding routine etc.
Assuming "average case": 90-120 Gal tank, Weekly water change, 28-30 Deg Celcius temperature, Feeding a mix of Pellets (I feed Hikari Cichlid Gold) and Prawns, once or twice a day.