Koi

• ExerciseLow

  A calm, unhurried swimmer — peaceful surroundings suit them best.

• GroomingEasy tank upkeep

  No grooming here — steady water quality and routine tank care do it.

• Living spaceMid-size tank

  Needs a mid-size aquarium with room to swim.

• Owner experienceSome experience helps

  A little know-how makes life smoother.

• Commitment25–50 years

  Plan for a long, loving relationship.

Health to watch: Ich (white spot) · Skin conditions · Fin rot

Koi (Cyprinus rubrofuscus var.) are ornamental carp developed in Japan in the 19th century from East Asian food carp; the name nishikigoi means 'brocaded carp.' They routinely grow to 60–90 cm and live 25–50 years, with the celebrated koi Hanako reportedly reaching 226. They are true pond fish, not aquarium fish. Koi need a large outdoor pond — realistically a thousand litres or more per adult — with excellent filtration and aeration. They are cold-hardy, tolerating roughly 2–30°C with an ideal of 15–25°C and a pH of 7.0–8.5, and they can overwinter under ice if the pond is deep enough. Sociable and long-lived, they are best kept in groups. Koi are omnivores fed floating pond pellets in the warmer months and little to nothing when cold, since their metabolism slows near freezing. They learn to feed from the hand and become remarkably tame. Their main health risks are parasites and bacterial ulcers, koi herpesvirus, ich and obesity from overfeeding; clean water, quarantine of new fish and seasonal feeding keep them thriving for decades.

• How active is a Koi?

  Low. A calm, unhurried swimmer — peaceful surroundings suit them best.

• How much maintenance does a Koi need?

  Easy tank upkeep. No grooming here — steady water quality and routine tank care do it.

• What tank size does a Koi need?

  Mid-size tank. Needs a mid-size aquarium with room to swim.

• Is a Koi a good fit for first-time owners?

  Some experience helps. A little know-how makes life smoother.

• How long do Koi live?

  25–50 years. Plan for a long, loving relationship.

• What health issues affect the Koi?

  Keep an eye out for Ich (white spot), Skin conditions, Fin rot. These are worth raising with your vet, along with any screening they recommend.

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