Jay stated the following in his article:
I think what aquarists need to be mindful of is not just what Jay stated, but also the overall mental health and stimulation that a fish will receive in captivity. Overcrowding is a known trigger of stress in fish, and there are researchers (a number of them) that now believe that finfish can experience things such as pain, they have long term memories, and can even experience forms of mental illness. Many of us have read about, or seen first hand this type of behavior, such as an adult fish losing their life long mate, and then moping in a corner and refusing to eat for days/weeks on end.
Stress
http://www.ncbi.nlm.nih.gov/pubmed/19949254
Mental Illness
http://www.bbc.com/earth/story/20150909-many-animals-can-become-mentally-ill
I think that one has to take in more than just the physical characteristics of the fish, and their environment, but also the psychological aspects of keeping an animal in captivity.