Quick referenceUronema marinum is a free-living scuticociliate that becomes parasitic in stressed marine fish. Causes red ulcers + rapid death; treat with formalin baths and improved water quality.
Symptoms
Yellow/red ulcer
Frayed/torn fins
Rapid breathing
Surface gasping
Refusing food
Bulging eye(s)
Hidden lesions under scales
Cause
Uronema marinum normally lives free in sea water. Becomes parasitic on stressed, weakened, or wounded fish. Common in low-salinity (under 30 ppt) tanks where fish are immunocompromised. Often strikes anthias + chromis after shipping.
Treatment options
Formalin bath (37%). Most effective. 45-minute bath in 1 tsp formalin per 1 gal aerated saltwater. May need 2-3 baths 48h apart for severe ulcers.
Furan-2. Backup for secondary bacterial infections. Treats opportunistic infections in ulcers.
Raise salinity to 35 ppt. Hyposalinity (under 30 ppt) makes fish vulnerable. Get back to natural reef salinity (35 ppt) gradually.
Improve water quality. Test ammonia + nitrite + nitrate. Reduce stocking density.
Always treat in a separate quarantine or hospital tank. Most medications are toxic to coral, invertebrates, and live rock biology. Consult an aquatic veterinarian for valuable fish.
Prevention
Maintain salinity at 35 ppt. Reduce stocking density - over-crowded tanks have higher uronema rates. Quarantine new fish (especially anthias + sensitive species).
Fatality + outcome
Moderate to high - 30-60% of infected fish die without treatment. Aggressive variant kills in 48-72 hours.