eBetta.com

Although Bettas do not require as much water as gold fish or other tropical fish, they should not be kept in a container or tank that is too small. Generally, anything below one gallon is too small for a Betta to live in and would require very frequent water changes – once every two days – that are stressful for the betta and too time-consuming for you. Remember, Bettas are living organisms that produce waste, which can accumulate to dangerous levels if the container is not large enough to accommodate their metabolic load.