I sure wouldn't keep a betta in a bowl that size, but they'll survive in them. I must admit that I've found they're happier in smaller surroundings than in a big tank, but they still appreciate some room to move and swim. Plus, if they're in that small of an amount of water, it's going to become fairly polluted very quickly. Bettas are piggy little eaters and you'd be doing water changes twice a day to keep him in clean water. (I know nobody does w/c twice a day for their bettas, which only means he'd be spending a good part of his time in ammonia/nitrite polluted water) I have bettas in divided 5.5 gallon tanks, though.. which means they're only in a couple of gallons of water each, and this seems more than adequate for them. Just my opinion.