Koi are among the most popular pond fish globally, capable of living 25-35 years, but welfare is frequently compromised by inadequate water quality, disease, and inappropriate stocking densities.
Koi in poorly maintained ponds suffer from ammonia toxicity, oxygen depletion, and infectious disease — all preventable with appropriate filtration and stocking density. As sentient vertebrates with complex social behaviors and long lives, koi welfare deserves the same attention given to mammalian pets. Poor water quality causes chronic physiological stress that reduces immune function and quality of life.