Just leave it. If you really want to remove it you can, but it's just a sign of a healthy betta.
the male betta fish makes the nest.
http://www.firsttankguide.net/betta.php
they can. but it is VERY rare. usually you would see a bubble nest.
The male Betta builds a bubble nest at the surface of the water. The ova(eggs) are fertilised under the nest then collected by the male in his mouth as they sink. He then places them in the nest where he tends them.
the Betta or Siamese fighting fish
No. The male betta makes the bubble nest, the female lays the eggs, the male fertilizes the eggs and then takes the eggs and places them into the bubbles of the nest. Most often he will then turn and attack the female i still present. The male will then tend to the eggs until hatched making sure to replace any eggs that fall out of their bubbles.
The male will make a bubble nest when the female is about to lay her eggs.
Place a female in close proximity where he can see her.
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.
Betta fish reproduce through a process called spawning. The male builds a bubble nest at the water's surface, then courtship and mating take place. The female releases eggs, which the male fertilizes, and he collects them in the bubble nest to protect them until they hatch.
it depends on if they have egg's in there but if not they don't get angry.
Before the mating period, the male betta will create a bubble nest, where the eggs will reside. Once the female is near, they will usually fight each other before finally mating. Once they finish, the male will take the eggs in his mouth and put them in the nest. If these are pet betta fish, then the female should be removed after an hour or two.