The problem with bowls isn't just the normally very small size of the bowl, but the shape itself. Being tapered toward the top, there is not enough surface area

The problem with bowls isn't just the normally very small size of the bowl, but the shape itself. Being tapered toward the top, there is not enough surface area to properly oxygenate the water for the fish. That in itself is reason enough to go for a tank in my opinion, but bowls are also more difficult to add proper filtration and heating to (although unfortunately people who house fish in bowls often don't get to the stage of even considering filtration or temperature regulation). Betta fish may not need as much space as some other fish, but they still should not be kept in bowls (no fish should). They can be very hardy fish, but just because they _could_ survive in a mud puddle or a tiny bowl without proper filtration doesn't mean they _should_ be kept in those bad conditions. They should be housed in an appropriately sized tank with low flow filtration and a heater (they're tropical fish and like warmer temperatures). I'm linking some articles on the topic of housing bettas below. * https://vetmed.illinois.edu/pet-health-columns/betta-fish/ https://vetmed.illinois.edu/pet-health-columns/betta-fish/ * https://bettafish.org/faq/do-betta-fish-need-a-filter/ https://bettafish.org/faq/do-betta-fish-need-a-filter/