Would it be cruel to lock you into the small powder room of a mansion for the rest of your life?
Unless the container is 1g, the betta should not live in it perminately. Regardless of tank size and airation, he's still in the little room of a big house and he wont do too well in there unless he can move around. I suggest buying him his own bowl or tank, or releaseing him into the main community (if possible). If you dont have an immediate home for him, he'll be just fine in the little cube, but he cant stay in there for-ever.