Auratus's are mean....but when Puma got a J. transcriptus (about 1/3 the size of the auratus at the time) the transcriptus killed the auratus. My opinon about the meanest cichlid is simply that it depends upon the individual fish. There is a difference between how strong and powerful a fish is, and being mean. You could have a Discus who was the meanest SOB anywhere, but they can't do much damage, if it pissed off an Oscar, the oscar would probably kill it, and not nessecarily be meaner than the discus, it just can dish out more damage. That being said though, attitude is 90% of the game. I've been told by one of the LFS owners here that he put some ghost shrimp in with his Fire Mouths, one of the shrimp lived, and the FM was actually afraid of it. The FM would come over and start acting like it was gonna make a snack out of the shrimp and the shrimp put his claws up, and rushed the FM. So the FM left the shrimp alone, even though it easily could have just eaten it. IMO its all a matter of the particular fish.