Koi Floating on Side: Swim Bladder or Something Worse?

Understanding the Symptom

A koi floating sideways (listing) but otherwise alive suggests buoyancy dysfunction. In a heated Montana pond, winter cold-congealed fat is unlikely. The recurrence after temporary improvement in shallow water points to a chronic issue.

Probable Causes

1. Swim bladder disorder: Infection, impaction, or physical damage affects gas regulation.
2. Intestinal blockage/constipation: Common from low-fiber diets or overfeeding.
3. Bacterial infection: Aeromonas or Pseudomonas can invade the swim bladder.
4. Parasites: Rare, but possible.

Immediate Actions

• Isolate in hospital tank: 20+ gal, cycled filter, aeration, matched temperature.
• Fast 3 days: Then feed shelled, cooked peas (fiber) or medicated gel food.
• Water quality: Pristine, 0 ammonia/nitrite, pH 7.2–7.8.
• Salt bath: 0.3% (3 g/L) for 10–15 min daily if bacterial suspected.

When to Consult a Specialist

If no improvement in 7–10 days, consult a koi veterinarian (koivet.com or local aquatic vet). Advanced diagnostics (X-ray, ultrasound) may be needed. Do not guess with heavy antibiotics—they crash biofiltration.