Whenever you feed live food (worms, fish, amphibs, mammals), you're taking a chance that you'll transfer parasites to your snake. I admit that I occasionally do it, but I also check their feces for signs of parasites. You could reduce the chances of transferring parasites by freezing the fish for at least 3-4 days before thawing them and feeding them to your snake. I do this MUCH more often. Without knowing the species of "minnow" it's hard to say if they would have the thiaminase enzyme to which Justin is referring. If you fed them sparingly (every 3rd or 4th meal at most), they wouldn't cause a B1 deficiency, even if they contained thiaminase. I'd stay away from very spinous fish, like stickleback, catfish, or bluegill though.

Rick