About 10 people have told me so far that I’m crazy to think that my fighting fish is breathing at the top of the tank. Since he always does it when they’re not looking, I had to google it. Here’s what I found:
Siamese Fighting Fish (Betta Splendens)
Even though Bettas do well in waters low in dissolved oxygen, that does not mean they require less oxygen than other fish. Bettas have a special respiratory organ that allows them to breath air directly from the surface. In fact they inherently must do so. In experiments where the labyrinth organ was removed, the fish died from suffocation even though the water was saturated with oxygen. For this reason, Bettas must have access to the water surface to breath air directly from the atmosphere.