Yup you should know where your nightcrawlers came from, but if u stil arent sure and you want to feed them to ur fish alive, you should rinse them well using tap water and allow them to soak in a pail for 6hours, we call that method here in the phil "lamming".. Live foods are hell way nutricious than the average pellets. Anyway jack dempseys are tough. So dont wory too much.