I am also clueless, just killed more rays in more ways than most of you guys!
med...Panacur probably.
I have killed some and saved some with Levamisole. With some meds it is important to keep your water hyper clean and pH neutral. Toxicity increases as pH lowers
If you've killed more then I'm sure you know more.

Still keeping any?
I know with every year that passes it gets harder and harder to justify. Guess some people have luck and sume just dont?