Seriously should not compare humans to fish... no disrespect, but the fish is ALIVE, and if he was unhappy, he would be stressed, if he was stressed, he would have had health issues and would not live so long.
Obviously the keepers are doing something right... How many ppl with 2500G tanks can keep one alive for 39 years?!
But if we keep comparing fish to humans, then stop putting WILD animals inside a house and leave them in the rivers, lakes, oceans they belong in.
And hes 39 years old lol off course hes not going to be all cheery.