Public aquariums house millions of fish for education and conservation. Fish welfare in aquarium settings involves water quality, space, social needs and enrichment that visitors rarely consider.
Fish welfare in public aquariums has historically received less attention than mammal or bird welfare despite fish representing by far the largest proportion of animals held. Water quality management is the most critical welfare parameter: even brief excursions in ammonia, dissolved oxygen or temperature outside species-specific tolerances cause acute stress and can be lethal. Tank size adequacy for highly mobile species including sharks, rays and large pelagic fish is frequently debated. Schooling species kept in insufficient numbers show abnormal behaviour from social deprivation. The collection pressure on wild marine fish populations from the ornamental trade affects both conservation and welfare through mortality during capture, transport and acclimation. Aquariums that prioritise captive-bred species and maintain high welfare standards through rigorous water management contribute to species conservation without these costs.