I currently have two show tanks set up for mixed African American cichlids with inhabitants from CA/SA, Malawi, Tang and Victorian. Water requirement is compatible but there is huge size difference from 11 inch CA to 1 inch tangs. To manage aggression, I picked only big gentle CA/SA in company with small aggressive Africans (minus hyper aggressive Mbuna). Also, I picked males only to prevent pairing except for the smallest Tangs which I provide rock piles to hide and make babies. There is peace and harmony in both tanks and hope it is sustainable as there is still growth left for the CA/SA.
I had a mix tank setup with a Red Bay Snook, 4 Convicts, 3 Venustus, 2 Red Forest Jewel, an Ellioti, a Pink Firemouth, a Cobalt Blue Cichlid, 2 Super Green Texas and various other non-cichlids. Somehow it worked out. Will find my old pics/vids if I can.