I have never tried to keep a Seminatrix in captivity myself, but I have heard from several people who have that they are almost impossible to keep alive. Much harder than Nerodia, as hard or harder to keep than Farancia.
I caught one the other day, a Seminatrix pygaea, a gorgeous neonate, and I was so tempted to keep it....
In the wild they eat sirens and salamanders, which is a difficult diet to replicate in captivity. And they hide all the time. Anyway, good luck.