FRESHWATER disease

Bacterial gill disease (Flavobacterium branchiophilum)

Reviewed by the Fast Aquatics husbandry team · Updated May 2026
Quick referenceBacterial gill disease (Flavobacterium branchiophilum) is a common freshwater bacterial infection of fish gills. Causes rapid breathing + flared gills; treat with antibiotics + clean water.

Symptoms

Cause

Flavobacterium branchiophilum bacteria proliferate in poor water quality - high ammonia, high organic load, overcrowded tanks. Common in pond systems + commercial farms.

Treatment options

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

Avoid overstocking. Maintain water quality. Clean filter media regularly. Quarantine new fish.

Fatality + outcome

Moderate - kills 20-40% of stock if untreated. Stressed fish die fastest.

Related

Full disease database · Symptom matcher · Q&A library · Glossary · QT timeline calculator