BSFL will eat just about anything, they are very easy to gutload. Silkworm ONLY eat mulberry/mulberry "chow," which makes them difficult to keep and raise longterm if you don't have a mulberry tree
Apparently my brother already has a special tote of some sort for breeding bsf! I'm going to get that cleaned out over the weekend and ironically we have two mulberry trees one everbearing and one I guess not everbearing lol! My brother is a organic health nut