Clostridium difficile (Prevot), an obligate anaerobic bacterium, was isolated from a species of African cichlids, Nimbochromis venustus (Boulenger), displaying external signs of "Malawi bloat". In other animals, this organism is a known cause of intestinal upset ranging from diarrhea to a fatal colitis. The bacterium was isolated and identified in an anaerobe chamber utilizing media to enhance for the growth of anaerobic bacteria. Disease is cause by the production of two protein toxins, which contribute to fluid accumulation and cell necrosis. The organism isolated from the intestine of bloated fish was determined to be positive for both toxins. This bacterium, Clostridium difficile, is suggested as a candidate for the etiology of "Malawi bloat" in African cichlids and other aquarium fishes.