You can but there is a risk of transfering parasites from the fish to you snake though.
If you freeze and thaw them before feeding them to your snake there should be no problem, although the content in the fish of vitamin b may be broken down in the process. You can add vitamin b to the f/t fish and that problem is solved.
Some are more conservative/careful/afraid, call it what you want, than others regarding this issue. I would be reluctant to feed semiadult or adult minnows to my snake without freezing them prior to use. I am planning on finding some minnow eggs and let them hatch and grow in an aquarium. It is not nearly the easiest way to do it but I think it is very interesting to see their development. On the other hand I'm just a nerd
