Koi are ornamental carp fish that are popular in ponds and gardens around the world. They come in a variety of beautiful colors and patterns, including red, orange, yellow, white, and black. Known for their graceful movements and long lifespans, koi can live up to 50 years in the right conditions. These fish are often associated with good luck and prosperity in Japanese culture, and are considered symbols of love and friendship. Koi require careful attention to their water quality and diet to ensure they thrive in their environment.