Public aquariums provide education and conservation value but must maintain high standards of animal care for fish, invertebrates, and marine mammals in their collections.
Aquarium animal welfare is primarily determined by water quality, appropriate species-specific tank sizes, suitable social groupings, and absence of chronic stress from inadequate environment. Fish in undersized tanks show abnormal behaviors, reduced immune function, and injury from repeated wall impacts. Invertebrates including octopuses require appropriate space and complexity for their cognitive needs. The public aquarium sector has variable welfare standards, with leading institutions investing significantly in animal care and others prioritizing display value over animal needs.