There are many possible causes for Popeye.
Could be bacterial, could be internal pressure , could be viral, could be due to physical issues like a tumor.
Most common I would say is bacterial. The main bacteria issues that cause this are gram negative bacteria. I'd recommend treatment with either minocycline (Maracyn-Two) or kanamycin. I'd also dose Epsom salt to see if any pressure can be relieved from behind the eye. Popeye is normally a secondary condition of a primary problem. To fix the issue must eliminate cause for primary issue.
The antibiotics are a great place to start along with the epsom salts. Epsom dose to start it 1 tablespoon per 10 gallons. Dose the antibiotics as recommended along with water changes.
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