Zebrafish are increasingly used in biomedical research and their social housing needs are now recognized as essential for both welfare and research validity.
Zebrafish welfare research has accelerated as this species' importance in biomedical research has grown. As vertebrates with demonstrable stress responses and social behavior, zebrafish deserve application of the same welfare principles applied to rodents in research settings. Social isolation in zebrafish causes measurable physiological stress that is both a welfare concern for the individual fish and a methodological concern for researchers, as stress confounds experimental outcomes. The practical welfare improvement of group housing zebrafish is achievable without major facility redesign and improves both welfare and research quality simultaneously - a powerful combination for driving change.