Popeye (Exophthalmia)

When to act urgently

Breathing distress, rapid deterioration, inability to remain upright, major wounds or multiple deaths require urgent aquatic-veterinary or fish-health help. Check aeration and water immediately; do not wait to match a photograph.

What you may notice

• One or both eyes may protrude, become cloudy or show bleeding.

Possible causes and look-alikes

• Trauma, infection, eye parasites and gas supersaturation are possible. One affected eye does not conclusively establish injury.

Check first

• Record species, aquarium type, recent arrivals or changes, appetite, breathing, and how many fish are affected. Check aggression, injuries, filtration and aeration.
• Test ammonia, nitrite, pH and temperature; measure dissolved oxygen where possible and salinity in marine/brackish systems. Correct verified environmental problems using suitably prepared water, avoiding abrupt chemistry changes.
• Review recent handling, aggression and changes to water or plumbing. Observe whether other fish or organs are affected.

Treatment and correction context

• Marked swelling, blood, apparent vision loss or additional illness warrants prompt examination.
• Appearance alone cannot select an antibiotic. Assessment must distinguish local injury from systemic or environmental disease.

Record for your next step

Write down onset and progression, species, affected/total fish, recent introductions, feeding observations, dated water results with kit units, and every action or product already used. Contact the diagnostic service before collecting or shipping samples.

Sources and scope

Source checks: 2026-10-03. Educational editorial summary; no independent veterinary review.

• Merck Veterinary Manual: Disorders and Diseases of Fish

  Environmental disease, eye disorders and noninfectious causes of illness.

• Merck Veterinary Manual: Environmental Diseases

  Environmental causes of illness, including oxygen, nitrogen compounds and gas problems.

• UF/IFAS: Submission of Fish for Diagnostic Evaluation

  Case history and contacting a diagnostic service before collecting samples.