Well, to me, anything you can 1. have a heater in (mini heaters included) and 2. keep your fishy healthy in, go for it :) I've had a range of bowls, small tanks and up to 20 gallons. I definitely will say, that bowls take more work, small tanks take more work, and cycled tanks take less work >< Just my opinion :) So if you had a couple bowl bettas, you may not mind it. But as for me, I have 9 bettas, plus a job, and schooling lol. So 9 bowls or small tanks would be terrifying :p
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.