Instead of feeding the metro, feed with the prazi.
I also wonder if he's having issues with the low salinity?
This should work if you have an idea of the fish's weight. You can use general cure in the qt, but I believe you are still in copper treatment?Prazi has a variety of oral doses. The one I use is 50 mg prazi per kilogram of fish body weight for three days.
I also wonder if he's having issues with the low salinity?