You might have to subscribe..but I read it of course and they say among other things "You need to give fish something challenging every now and then..they need to explore. Higher oxygen content makes for happier fish. Never keep Bettas in less than a 2' tank. Move things around a little every now and then.
Based on a Scientific paper....
Based on a Scientific paper....
Fish Depression Is Not a Joke (Published 2017)
Fish can get depressed, just like you, and that could make them a good model organism for studying depression in people.
www.nytimes.com