Well, its supposed to be artsy. You can see a lot of the fish, and by shooting it so close I was trying to give you a kind of insight of what it might be like to be a fish in the tank. It also breaks a little from most other types of shots - a lot of bright shots where people overcompensate in iso or other methods to get brighter pictures
Furthermore, the focus is entirely on the fish rather than background or plants or anything else in the tank.
I like that betta pic. The betta is highlighted by lush colors and a great contrast with the black background. Everything important is visible, and everything else is left in the dark. It certainly draws my eye in.