Every wonder why that is? The old saying that we dismiss as myth certainly has some truth to it...'fish only grow to the size of their tank'. Don't believe me? Peacock bass are a perfect example. Look at the sizes of the bass being kept by 99% of the people on this forum in 200-400g tanks. They're runts compared to what you see in the wild. "But that's in the wild, not in captivity". Bullcrap. Look at the size of the bass in JohnPTC's 10,000g tank. They're freaking monsters. Fish DO grow to the size of their environment.
You don't see aros reach 4ft in captivity because we can't/don't give them the environment to reach their full potential. A 240g is hardly adequate.
But that's my point. No one except guys like johnptc should keep aros or peacock bass then by that rationale because a 300g is even too small for them. There is always going to be bigger pbass or aros somewhere in a bigger tank but that doesn't mean that specific fish is going to live longer than one in a 300g.