A lot of times pop eye is caused from some sort of trauma to the eye, a scratch, and can heal by itself. Other times an infection takes hold. And sometimes, it is air caught behind the eye.
If you already have the fish in the QT, I'd keep it there. The QT will allow the fish to eat and heal w/o any additional stress that can happen in the DT. Maintain excellent water quality in the QT, this goes a long way to helping a fish heal.
Make sure the expiration on the package was good, sometimes these sit around lfs's on the shelf for long periods of time.
If you this this might be bacterial-type of an infection. You can give the fish a few days in clean water before treating a second time. You can change brands if you believe there was some issue with the brand you previously used. Make sure you pick up a antibiotic that treats popeye. You can also try to treat the fish with antibiotic laced foods for two weeks and see how that goes.
sorry to hear ! cheers for trying to save him !
