Koi
Published
Koi are the pond fish. Large, calm and patterned in red, white, black and gold, they turn a garden pond into a slowly moving painting — and with good care they can outlive the people who first bought them.
From rice farms to living art
Koi are a domesticated form of the carp of East Asia. In the early 1800s, rice farmers around Niigata in Japan, who kept carp in their irrigation ponds as food, noticed fish with red and white markings and began breeding from them. Over generations this became an art. Koi were shown to the wider world at a 1914 exhibition in Tokyo, and today koi shows judge fish on body shape, skin quality and how clean and balanced the pattern is. The very best fish sell for more than a house.
Varieties
Breeders recognise dozens of varieties, each with a Japanese name. A few of the best known:
- Kohaku — white with red patterns, often called the first and most important variety.
- Showa — black with red and white.
- Goshiki — "five colours", with a net of dark scales over red and white.
- Ogon — a single metallic colour all over, such as gold or platinum.
- Ghost koi — a cross between koi and wild carp, with a metallic, shadowy look.
Koi patterns are never quite fixed: they shift as the fish grows, and a promising young koi can become ordinary as an adult, or the other way round.
A fish for a pond
Koi grow big and live long, so they need a pond, not an aquarium: a few thousand litres at the very least, deep enough not to freeze solid or overheat, with strong filtration since they eat and produce a lot of waste. They follow the seasons. In cold water their metabolism slows almost to a stop, and keepers stop feeding them until spring. Koi learn quickly who brings the food and many will eat from the hand.
Breeding
In late spring, as the water warms, koi spawn in a noisy chase among the plants, and a large female can scatter hundreds of thousands of eggs. Only a tiny share of the young turn out with good patterns, which is why breeders sort through huge numbers of fry to find the few worth keeping.