I'm glad your fish are coexisting; considering the size of both the aro and the ornate, I'd have thought the African cichlids and the bicolor shark would be gone by now.
I also have to stress the importance of a big tank, especially if you get an RTC. I don't think an RTC will be so harmonious, and the only thing I think it will be incapable of eating will be a full grown Pacu... but everything else in that tank will eventually be eaten. And Pacus have been measured at 40 inches, which makes a large tank all the more important. Good luck and I hope the harmony continues.