but yes, i attempted breeding with a larger female,she whooped his butt and he was hiding from her.i also had a very timid male get his butt whooped...she was thicker but not longer.i kept a few females in my angelfish/ctenopoma /gourami tank...and guess what? the females would puff up and attack as quickly as any male. i have learned all this from simple trial and error...i love bettas!
as far as the small containers are concerned, i think its a lot of crap...
i feel sorry for them,because its a tiny,sad world. BUT, the breeders in thailand raise them like that, ok? and they are expert at it! they ship gorgeous exotics all the way to new york and they come out of the bag flaring! i have kept mine in gallon jars with plant and black water/betta tea,changing the water half mid week, complete once a week.with distilled or filtered water, betta conditioner. they really are tough little guys and can survive a lot of conditions. and to be honest,they are happiest alone...they are annoying community fish. they are fighters. usually,you can keep a horde of females together if you want.or a horde of females and one male.