Pet fish are among the most commonly kept companion animals but receive inadequate care due to underestimation of their behavioral complexity and space requirements, with most commercial tanks far too small.
Pet fish welfare is the most overlooked area of companion animal care, with billions of fish kept in conditions that cause chronic stress, disease, and premature death. The cultural perception of fish as simple, low-maintenance pets has persisted despite growing scientific evidence of their behavioral complexity and capacity for suffering. Fish in bowls without filtration or heating, tanks that are too small, and with incompatible species suffer from ammonia poisoning, temperature stress, and social aggression. The welfare standard for pet fish should match the scientific understanding of their sentience rather than the convenience of keeping them in small, unfiltered containers.