Bettas are well-known for being able to live in a relatively small aquarium. This special feature is said to derive from their natural habitat in the Far East being shallow pools of water and small streams. They are being territorial fish and they are likely to stick to their little territory and not swim too far away.
In piece of information, you can keep your Betta in a bowl. However, Betta fish require as
1. Some moving space with a decent size tank. Even if you use a fish bowl, make sure it contains at least two gallons of water per fish
2. A larger tank is better, as it allows your betta more room to swim around and lets you enjoy a better display of its impressive tail and fins.
Betta desires contact to the top of the water, as they are able to absorb some amount of O2 from the water surface. Beta also need a stable warm water temperature that is mean you have to put a heater to heat the water. Some type of filtering and airing is also recommended, so all in all, creating good living condition for your betta fish means you need a decent size aquarium. If you use a fish bowl, it needs to be a large one.