The rule of thumb for ALL fish (not just betta fish) is about 1 gallon of water for each inch when measuring the length of the fish. So unless you are planning on using a gallon sized mason jar, it is best to not use one for an aquarium.
Fish Care Tips. There’s a reason people of all types love bettas. Sometimes called Siamese fighting fish, these feisty fish pack a lot of personality into a very small package and make great pets for almost every living situation.