Been thinking about this lately. Clearly fish that are not space-stressed are less likely to show aberrant or hyper aggressive behavior; yet if two fish are hell bent on mutual destruction, even a large tank doesn't help. So how big does a tank need to be to offer enough space that two fish can stay away from each other? I have a 450 ..... it's not big enough. Saw the 20,000 gallon tank on Long Island ..... that seemed big enough. So I guess it's somewhere in between. Been conceptualizing my next tank (somewhere in the 2,800 gallon range - 16' x 6' x 4'). Would that be big enough I wonder?