Koi are colorful fish that belong to the carp family, specifically the Cyprinus carpio species. They are often kept in outdoor ponds and are known for their vibrant patterns and colors, which can include shades of orange, white, black, and yellow. Koi are popular in Japanese culture, symbolizing perseverance and strength. These fish can grow quite large, sometimes reaching lengths of over three feet. Koi are social creatures and thrive in groups, making them a favorite among aquarists and pond enthusiasts. They require clean water and a balanced diet to stay healthy and vibrant.