Nerodia (watersnakes) eat a lot of fish, but in my experience they are not all that active. They also get pretty big, crap everywhere and bite a lot. I think some of the folks on this forum keep them and can probably give you a totally different first-hand account of nerodia keeping. This is just my opinion.

I've also heard of Aheetulla (Asian vine snakes) eating fish. They are not at all active and are nearly impossible to keep alive if they are not the center of your attention.

If you leave agkistrodon out of the equation (as you should). I think that sums it up.

Anyone else want to throw their hat in?