Frozen is for sure much easier & more convenient to ensure you have the best size on hand to feed your pet snake. Pet stores often run short of live sizes you need. But at least you have him eating regularly- all in good time, you'll get there. Some snakes (like BPs) may balk at changing the type of rodent also- rats & mice smell & taste differently, otherwise you could easily substitute a mouse of the right size for the rat pup they were out of. They tend to prefer mice, so if you can keep him on rats, it's more convenient for when he's bigger because rats come in bigger sizes that "fit" an adult BP. If you were still feeding mice then, it might take several, & then some snakes will only eat one item, even if it's too small.LOL, some snakes can be goofy...