Zebrafish are used in millions of experiments globally. Their social nature and specific environmental requirements mean housing standards have significant welfare implications.
Zebrafish welfare in research requires recognition that these are genuinely social, cognitively capable fish with environmental needs that standard barren laboratory tanks do not meet. Social isolation increases stress indicators and alters experimental results - a finding that simultaneously argues for welfare improvement and better science. The regulatory gap for embryos under 5 days reflects uncertainty about sentience development rather than evidence of absence. High-welfare zebrafish research facilities provide appropriate group housing, environmental enrichment, and minimise procedures causing pain or distress.