Common Koi Diseases & How to Treat Them
Most koi health problems trace back to stress and poor water quality. Catch issues early and most are very treatable.
Parasites (flukes, ich, costia)
Signs: flashing, rubbing, clamped fins. Treat with a broad-spectrum anti-parasite treatment and check water quality.
Ulcers & bacterial infections
Signs: red sores or open wounds. Isolate the fish, improve water quality, and treat promptly — severe cases may need a vet.
Fin rot
Signs: ragged, receding fins. Usually a water-quality issue — test and correct parameters, then treat.
Prevention is everything
- Quarantine new koi for 2–4 weeks before adding them to your pond.
- Test water weekly with a master test kit.
- Don't overfeed or overstock.
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