GATF vs Armatus

[Chicxulub]

So this would mean the armatus would be more aggressive and would kill the ATF? What if they were same size though? Even though the armatus is meant for eating smaller fish can it still take bite out chunks?

Simply put, anytime you mix fish with the fearsome armament that these two possess, there is always a chance for a disaster to happen. Both fish are equally able to kill the other, the likelyhood of the fish trying is dependent on what you feed them and the fish's individual personality.