I am taking it that a rice box to a ferret is the same as a sand box to a child. Since I have been read FML I know that many are worried about rice in a rice box for reasons. I have changed the rice box to a popcorn box. (unpoped) It does not swell as I know from growing my own and having to dry out or add moisture depending for perfect poping levels needed. A 50 pound bag cost about 2 dollars more than the rice. My guys love it. Lona [Posted in FML issue 4015]