Koi and ornamental fish in garden ponds are susceptible to disease, predation, and seasonal welfare challenges that require active management by owners.
Ornamental fish including koi exist in artificial pond environments where their welfare is entirely dependent on owner management. Poor water quality causes chronic physiological stress, disease susceptibility, and impaired welfare. Heron predation causes both direct welfare harm to taken fish and persistent fear states in pond populations. Seasonal challenges including summer oxygen depletion and winter ice cover require active management to prevent welfare crises. As long-lived animals with demonstrable learning capacity, koi represent welfare-significant companions whose needs merit serious consideration.