Koi are among the most popular ornamental fish worldwide, but their welfare needs are frequently misunderstood, leading to chronic stress and preventable disease.
Koi welfare depends critically on water quality, space, and disease management. Many owners underestimate the filtration capacity needed for high-density koi ponds, leading to chronic ammonia and nitrite stress. Koi are social animals that benefit from group housing, but overcrowding negates this benefit. Biosecurity when introducing new fish is essential to prevent disease outbreaks. Recognising early disease signs and having access to a fish veterinarian are key components of responsible koi keeping.