Water quality is the single most important factor in koi health. Understanding and maintaining proper parameters prevents the vast majority of disease issues.
Critical parameters and ideal ranges:
pH: 7.0-8.4 (stability is more important than the exact number)Ammonia: 0 ppm (toxic at any measurable level)Nitrite: 0 ppm (toxic at any measurable level)Nitrate: Below 40 ppm (lower is better)KH (Carbonate Hardness): 80-120 ppm / 4-7 dKH (buffers pH stability)GH (General Hardness): 60-200 ppmTemperature: 65-75F ideal (koi survive 35-85F)Dissolved Oxygen: Above 6 mg/LTesting frequency:
New or cycling ponds: test dailyEstablished ponds: test weeklyBefore and after any treatment: always testAfter adding new fish: test daily for a weekWhen results need prompt escalation:
Confirm unexpected ammonia, nitrite, pH, or temperature changes with a current test methodReview source-water, filter, weather, feeding, and stocking changesSeek qualified pond or aquatic-veterinary guidance before choosing a chemical or medical response