Bacterial Population of Diets for Aquarium Fishes

Abstract

Twenty-five commercial diets formulated and offered for feeding to aquarium fish were examined to determine their microbial burden. The total count of aerobic mesophilic bacteria in 24 of the feeds ranged from 9 × 102 to 1.3 × 106 per gram of diet. Twenty of the diets contained from 7 × 102 to 2.4 × 105 bacteria per gram able to grow anaerobically. One of the feeds was sterile. Species from the genus Bacillus were most numerous, but species of Clostridium (including C. perfringens), enterococci, and members of the Enterobacteriaceae were also present in significant numbers. The fish diets supported the growth of a wide variety of bacteria known to be pathogenic to fish and to man.