Koi fish are colorful varieties of carp that are often kept in outdoor ponds and water gardens. They are known for their vibrant colors, patterns, and sizes, which can reach up to three feet in length. Koi are originally from Japan, where they have been bred for centuries for their beauty and symbolism. These fish are not only admired for their appearance but also for their longevity, with some living over 200 years. Koi are social creatures that thrive in groups and can be trained to eat from their owner's hands. They require clean water and a balanced diet to stay healthy.