Bacterial disease is the most common infectious problem of ornamental fishes, and most bacterial infections are caused by gram-negative organisms. The majority of bacterial fish pathogens are natural inhabitants of the aquatic environment, whether it be freshwater or marine. Extrinsic stressors, including shipping, crowding, poor water quality, and inadequate nutrition, may predispose an ornamental fish to bacterial disease. This article reviews the important bacterial pathogens of ornamental fish in a systematic manner, discusses the problems of over-the-counter antimicrobial compounds and antibiotic resistance, and reviews treatment and management options.