if your already feeding him fuzzy rats then i would just stick to rats only. no mice. you want to increase his feed size to a small rat when the girth of the snakes mid-section is about the same size as its prey. Also you can change to frozen whenever you would like just make sure you research on how to do it correctly. i would provide you with a site but i dont know much bout feeding F/t .. i have always just fed live... I like to keep my animals wild in some way