I always use crumbles (usually starter,but I think any kind would be fine) and mix in some oatmeal from my kitchen. I have been doing it for the three years since I started. I like not having to buy something else to store, just for the mealworms. They are SO easy!! You don't have to be picky or even consistent with them!! I once left mine in a closet in the garage for MONTHS without any care at all!!! I just knew they were goners.....but there were actually plenty of live ones in there, all stages, so I refreshed their containers with some oatmeal and potato, and they were thriving again!!! I have always had tons of animals of all sorts, and this is probably the easiest thing I have done for any of them!!