What are koi?
Koi are ornamental carp selected for color, body, pattern, skin quality, and overall presence. Their story begins with the long history of carp in East Asia and develops into the modern Japanese Nishikigoi tradition. For the keeper, the foundation is less romantic but more important: stable water, enough space, good filtration, oxygen, and patient observation.
| Foundation | Practical starting point | Why it matters |
|---|---|---|
| Water volume | Plan at least 250 gallons per adult koi; more is easier. | Dilutes waste and reduces temperature and pH swings. |
| Water testing | Ammonia 0, nitrite 0, stable pH, adequate KH, oxygen above 6 mg/L. | Most health problems begin as water or oxygen stress. |
| Filtration | Separate mechanical solids removal from biological filtration. | Clear water alone does not prove ammonia and nitrite are safe. |
| Quarantine | Observe new koi separately for several weeks. | Prevents introducing parasites or serious disease to the pond. |
