Ok first I'd like to say if a 12inch dovii is able to hunt, survive, breed etc. then it can be put in the ring with a 12' butterkofri. you can't put human traits on a fish. No it is not full size but itis capable of holding territory & eating,killing fish its' size. I had a 3' v.argentea do damage to 3 haitiensis & 2 other argentea just because he wanted them dead he was kept by himself for sevral years until given to a friend. Fish are not mammals they are at any size equal to any other fish of similar size. remember a 12' dovii is bigger then a 5 inch neet. nematopus which is in my book one of my top 5 most aggressive. The list goes H. fasciatus(ok it is african), Chauco intermedium, v. argentea, neet. nematopus, & nandopsis grammodes. You figure parachromis species do tend to start problems(they eat other fish for a living so view all as potentail prey) but a good lip lock with an amphilophus, veja, or chauco species will usually leave their lips split. I never had a butter hold their ground if the veja kept attacking same with dovii,managuense, & motoguense like a previous member said the zailosus held off the dovii but actually it probaly would have beat it by now if not for the 3rd party interfering so there is no actual one on one fight in the 150 gal. one on one I'd place my money on anything but a parachromis species against any agressive amphilophus,veja,or chauco. They are used to overpowering prey not standing up to a fight. don't get me wrong if the fish backs down it is dead as it will now be considered prey by the parachromis. Don't get size confused with aggression. i kept & fought fish when I was young. so I seen severums fight for their life 7 live against managuense. Thor. meeki & roberstoni hold their own against motos. ; geo. stendachneri stop an amph. labiatum as long as the butter jumped in before the labiatum focused on the geo. I will also give credit to neolamprologus leluepi & cylindricus(yes they are african) I kept all my fish mixed. This is the U.S. after all one big melting tank.