But they're only 18", and don't have big teeth.Bite size for an arapima (9ft), ATF(5ft) or Aimara(4ft). Now that I think about it, I'm not sure the hoplias aimara or goliath could be a threat to the arapima.
A lot depends on temperment. I remember an MFK thread that I can't find about a Buttikoferi pair that successfully defended and raised fry in an arapaima tank.
I’d feel the top fishes would be the Aimara, Goliath Tiger Fish, Arapima, Golden Dorado, and Alligator gar
The gar would remain because of its size and armor. I feel the arapima would play the same role as just not being offensive. On the other spectrum, while the Gatf has the equipment, I don’t think it has the attitude to back it up. The Dorado would fare better as it has the confidence and ability. Above all, I believe a aimara not only has the weaponary, but there isn’t a fish that has the attitude and fearlessness of an Aimara. The fish just simply won’t back down no matter what’s in front of it. And the teeth on it make it all the more effective. That’s my 2 cents on all of this.