The welfare needs of companion fish, the gap between typical keeping conditions and genuine requirements, and evidence-based care for common aquarium species.
Companion fish welfare is systematically undervalued relative to mammalian pets, partly because fish pain and stress are less visible and partly because cultural attitudes toward fish sentience lag the scientific evidence. Fish kept in bowls without filtration, in uncycled tanks with ammonia toxicity, or alone when they are social species suffer in ways that are real but largely invisible to owners. Evidence for fish cognition and pain experience has strengthened significantly over recent decades. The welfare standard for companion fish should be as high as for any other pet — appropriate space, water quality, social environment, and enrichment suited to species-specific needs.