I have a 18inch normal ball. I heard I should be feeding him young mice, not pinkies anymore.

Anyway, the petshop didn;t have any small mice, so I bought a hamster to feed him. He has eaten 2 hamsters now, is that ok? I know they probably closer related to a gerbil, but I also don't want to get him stuck on hamsters, and when he's full grown, I have a little problem.

Thanks in advance