A kind of carp · also called Koi, Nishikigoi, Japanese carp

About
A koi fish is an ornamental carp breed that can grow to nearly two feet long in backyard ponds.
Koi are domesticated varieties of carp selected over generations for distinctive colors and patterns. Female koi generally grow larger and rounder than males, especially during the breeding season. Growth depends heavily on water temperature, food supply, and pond volume, with some specimens growing past 30 inches (0.76 m) in spacious settings.
From Wikipedia
Koi , or more specifically nishikigoi , are colored varieties of carp that are kept for decorative purposes in outdoor koi ponds or water gardens.
Read more on Wikipedia →Text from Wikipedia’s “Koi” article, CC BY-SA 4.0.
1 on the site
Weight
7.72 lb (3.5 kg)
Quick answer
A typical adult koi fish measures about 22 inches (0.55 m) long, 7 inches (0.18 m) tall, and weighs roughly 7.7 pounds (3.5 kg). This puts it at about the same weight as a domestic house cat.
Typical figures, the same ones every comparison on the site uses; real ones vary.
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