If anyone knows the cure for an inactive fish please share it with me!
I have a male that lays on the bottom of his tank nearly every hour of the day. He eats normally, but otherwise shows no real signs of activity.
I have tried anti-bacterial medication, de-wormer, live foods, salt treatments, flaring sessions, and Indian Almond Leaf extract. At the moment I've wedged his tank in between one of my hyper-aggressive males and a female, and still nothing.
If your tank is cycled and you're only registering 5ppm of nitrates, your water change percentages should be fine. Going by your readings, it definitely isn't a problem with water quality.
Perhaps the bout of popeye has compromised your male's immune system in some way. Mine has a badly bitten tail that has never shown signs of re-growth and I wonder if there is some issue with the immune system causing it.