:V some of my bettas are in tanks under 2 gallons. i try hard not to do anything under a gallon, but sometimes, you're just not able. as long as the tanks are heated, and water is changed regularly, it's fine.
i mean, how do you think breeders keep their bettas? some, in mason jars WELL under a gallon. some in custom built barracks with each betta having .5 gallons. our pets do well in bigger tanks, but as Karpediem said, breeders can't keep their bettas in bigger tanks. it's not logical and wastes space. x-x