If goldfish don’t belong in bowls, certainly something does, right? Bettas have often been kept in small containers, and it’s true that they probably aren’t as miserable as a goldfish in that environment.
But even bettas need space and hiding places—and nourishment. Companies have often tried to market small bowls, vases, and itty-bitty tanks as if they’re appropriate for small fish like bettas. But any small fish bowl will quickly become full of fish waste and uneaten food, which makes the tank dirty and also unhealthy for the fish, so some of these sellers will claim that you don’t need to feed the fish, or that you only need to feed it a very small amount.
For a while, there was a trend of keeping a betta in a vase with a plant like a peace lily. Supposedly the fish will nibble on the plant roots, and the fish’s excrement will nourish the plant. This is, and always was, bullshit. Bettas are carnivores and eat bugs. Nibbling at plant roots is the equivalent of a person trying to eat the leather of their shoes in a famine. If you love your betta, miniature aquatic shrimps, or any other small aquatic pet, do it a favor and set up a five-gallon tank.