i had a 1.5 gallon bowl or what ever. i kept one minnow(may have been a guppy it was very small whatever it was, 1/2 size of a regular fancy guppy) in it, i think it was probably ok for it.
10 gallons are 10$ at walmart...... people just are not interested thats why they buy a bowl. That so they can carry the whole thing to the sink and pour all the water down the drain.