Whether or not a human agrees or disagrees with tank size in many ways isn't relevant.
Because the fish are the ones that will tell you.
If the tank is too small, aggression issues or stress related disease will occur,
I've have seen many posts by people who say a 50 or a 75 gallon tank, is by their standards, large enough for this or that fish, but often there are posts a few months later by the same people wondering why this fish or that fish is killing one that was fine yesterday, or wondering why do my fish have HITH .
The fish are pretty obvious about what they do or don't need.