check the PH in the water,
it looks like they have a big bubble in their side
Betta are social fish. There is nothing wrong.
It probly is a female
Female Betta fish do not make bubble nests.
http://www.firsttankguide.net/betta.php
Place a female in close proximity where he can see her.
they can. but it is VERY rare. usually you would see a bubble nest.
The male will make a bubble nest when the female is about to lay her eggs.
It's not something on the fish. He will blow a nest of bubbles on the surface of the water that hold up the eggs.
it depends on if they have egg's in there but if not they don't get angry.
Male Betta fish make bubble nests when they are happy ^^ I have only had male Betta fish and after a day or two of playing with them and feeding them or even just talking to them they make their nests to show you that you made them happy.
because if the eggs were left unguarded, other fish would eat them. and it makes it easier for the dad to clean.