inject a couple worms feed it to the ray.dont over do it.i bought eye droppers and poke a hole in a nightcrawler than empty eyedropper in the worm.I found when they tasted the prazi pro they didnt eat anything for a bit and were very cautious i tried to do it a few more times and you can tell that they dont like it.It wont take much to kill a parasite.Dump some prazi on a leach or blackworm and see what happens