I watch my betta's sleep sometimes and they'll hang to the top and take little breaths every ten minutes or so but they don't really react. Kai sleeps near the heater and Lelouch well...He sleeps wherever the heck he wants to on that night. I don't watch him sleep that much since he's fond of trying to go for my face whenever he wakes up and realizes I'm in view. He will leap to get me.
So...Yeah betta's do still need to get air but it depends on the fish. When Kai was feeling his worst he was at the bottom of the tank and didn't care he had to make a frantic run to the surface...He wasn't sinking either he was going for that stupid mossball.
Lelouch of the Petsmart Rebellion - Orchid VT
Yugi - German Sheperd/Pitbull mix. The real King of the house.