The influence of an aquarium on resident behavior and staff job satisfaction in three dementia units was examined. The sample consisted of 71 individuals with dementia and 71 professional staff. A pretest–posttest design was utilized. Baseline resident behavior and staff satisfaction were obtained, and an aquarium was introduced into the setting. Post-behavioral assessment and job satisfaction surveys were completed. Residents’ behaviors improved along four domains: uncooperative, irrational, sleep, and inappropriate behaviors. The overall residents’ behavior score was significantly improved after an aquarium was introduced, F = 15.60, p < .001. Their mean disruptive behavior score decreased from 67.2 to 58.2. The staff’s satisfaction score significantly improved, F = 35.34, p < .001. Pretest to posttest mean scores improved from 149.4 to 157.9. Aquariums are an innovative way for animal-assisted therapy and nature to be introduced to specialized dementia units in long-term care.