Koi and ornamental fish are kept by millions of people globally, but their welfare needs — clean water, adequate space, species-appropriate companions, and veterinary care — are frequently misunderstood or neglected.
Ornamental fish welfare is an underrecognised area where the perception of fish as simple organisms has historically allowed substantial neglect. Koi in particular are long-lived, individual animals capable of recognising their keepers and responding to environmental change. Their welfare depends on water quality management, appropriate stocking density, veterinary care when ill, and adequate pond or tank volume. The aquatic veterinary specialty has developed effective diagnostic and treatment protocols that significantly improve outcomes for sick koi.