Recognizing Columnaris
White or grey fluffy patches on mouth, fins, or body. Often mistaken for fungal infection but is bacterial.
Mouth lesions can spread across the head in hours. Gill lesions cause rapid breathing and surface gasping.
Aggressive Treatment
Furan-2 (nitrofurazone) or Kanaplex are first-line treatments. Start within hours of identification.
Lower water temperature to 75°F — bacteria thrive in warm water above 80°F.
- ✦Quarantine immediately — columnaris spreads through water
- ✦Increase aeration — antibiotics deplete oxygen
- ✦Test water — columnaris often appears in tanks with poor water quality
Common Triggers
Damaged fins from net injury, fights, or rough décor.
Stress from temperature swings, ammonia/nitrite spikes, or aggressive tank mates.
Tank-Wide Treatment
If multiple fish show symptoms, treat the entire tank. Single-fish treatment in a community tank often fails — bacteria reinfect.
After treatment, deep-clean décor, replace 50% of water, and observe for 14 days before considering tank cured.