Koi are family-friendly and lovable pets that provide peace and relaxation. The prerequisite is that humans understand their needs and properly design their living environment. Often, the demands of the animals must take a backseat to the aesthetics of the garden and the desire for crystal-clear water. With the tips provided here, both can be achieved: healthy, vital animals in clear water. Therefore, this guide focuses primarily on the needs of the Koi and the environment we must create to prevent them from getting sick, rather than primarily on treating diseases and recognizing them. Drawing from over twenty years of practical experience as a veterinary specialist for fish, the author answers the most frequently asked questions and demonstrates how to recognize diseases in a timely manner.