Congrats on keeping the Scomb healthy! How big is he? Mines 8" @ 18mo. lives wil 3x Cudas, Brycon, PBass, Datniods, BGK, Firemouth, 2X Chaleus, whip tail cat. Tank Size is gonna govern what you can cohab and how many. If the Scomb is in the 50/55 odds are cohabing isn't gonna happen. If you move up to 125 long or larger you'll start to get some options. Even tho the Scomb might seem like king of the hill at the moment the Green Terror and Eureka Red Jacobfriebergi will both easily out grow the Scomb, perhaps not in length but in overall size. Unfortunately your cohabing 3 fish that all share a very common link - all 3 fall victim to stress rather easily.