, if the fish appears healthy, active and is not hiding, it would imply happy or well-being, not so much happy as in jubilant.
However my percula clown often plays in the ph
current, bobbing around back and forth, up and down for long periods of time (when he could swim elsewhere). This type of behavior does not seem natural or programmed, and would seemingly serve no purpose in the wild. It actually looks like play, like he's having fun. FWIW
he appears happy as a result. My clarkii does not play, but does not appear unhappy.