Columnaris (Saddleback Disease)
Highly contagious bacterial disease. Appears as white/gray patches, often starting at the dorsal area or mouth. Sometimes called "cotton mouth" or "saddleback". Progresses rapidly, fish can die within days.
Check these symptoms in your tankSymptoms of Columnaris (Saddleback Disease)
- White cottony patches
- Open sores or ulcers on body
- Ragged or fraying fins
- Rapid gill movement / labored breathing
- Lethargic / hiding more than usual
- Refusing to eat
How to treat Columnaris (Saddleback Disease)
- Isolate affected fish immediately
- Kanamycin + furan-2 combination is most effective
- Lower temperature slightly (reduces bacterial growth speed)
- DO NOT raise temperature, worsens columnaris unlike ich
- Add aquarium salt to reduce osmotic stress
How to prevent it
- Quarantine all new fish
- Avoid high temperatures (>78°F increases virulence)
- Reduce crowding and net stress injuries
Conditions with similar symptoms
Open sores or ulcers on the body caused by Aeromonas or Pseudomonas bacteria. Often secondary to wounds, handling stress, or poor water quality. Ulcers can deepen rapidly and become life-threatening.
Bacterial (and sometimes fungal) infection affecting fins and tail. Usually secondary to stress or poor water quality. Fins appear to disintegrate from the edges.
Fluffy white or gray cotton-like patches on body, fins, or around mouth. Often secondary to wounds, fin rot, or poor water quality.
Not sure? Use the symptom checker
Many fish diseases look alike. Pick the symptoms you see in the free fish disease checker to compare likely causes, or scan a test strip to rule out a water problem first.