Unlike many other fish, bettas can live in a fish decent size bowl without a filteration system. Small bowls used in fish shops are not suitable for bettas. This bowl should be cleaned at least once a week. If bubbles appear at the top of the tank, that is a sign that the male betta is healthy. The bubbles are in fact the nest for male betta. When cleaning it, make sure to put pre-filtered (reverse osmosis) water and water conditioner in.
A boy and girl betta usually don’t get along in the same tank together. If you are breeding two bettas, get a girl equal or smaller than the boy. You should also read extensively about breeding bettas – it’s not easy. You must also learn how to hatch baby brine shimps so the fry will have some food to eat.
It is safe to put several female bettas in the same tank, but NEVER put two male bettas together. These fishes are territorial and will fight to the death. It is also safe to put any gender of betta with another type of smaller, less colorful fish. Female bettas form a pecking order, so having only 2 female bettas in a tank is not a good idea.