Management of ornamental fish diseases

Ornamental fish keeping is one of the most popular hobbies in the world. The aquarium fish trade has  a turn over of    5 billion    US dollars and an annual growth rate of 8%.  India’s share of the ornamental fish trade is estimated to be Rs.158.23 lakhs, which is only 0.008% of the global trade. About  80% of Indian market for ornamental fish is of freshwater origin and the rest are marine and brackish water fishes. About 600 ornamental fish species have been reported worldwide and Indian waters possess a rich diversity of over 100 indigenous varieties. The popular live bearer species include guppies, molly and sword tail, whereas egg layers include gold fish, koicarps, barbs, rasboras, clarius, retras, catfishes etc.

                Disease has become a critical factor hampering the development of ornamental fish culture in many countries. Diseases of ornamental fishes are caused by parasites, fungi, bacteria and viruses.

                The most commonly observed viral disease of ornamental fishes is called Lymphocystis disease. This disease is caused by an iridovirus, which infects connective tissue cells of the fish.

                The majority of bacterial infections are caused by gram-negative organisms such as Aeromonas, Citrobacter, Edwardsiella, Flavobacterium, Mycobacterium, Pseudomonas and Vibrio. The majority of bacterial fish patogens are natural inhabitants of the aquatic environment. Over 805 of the gold fish contained Pseudomonas, Citrobacter and Escherichia.

               Among fungi, Saprolegnia is the mot common genus affecting tropical fishes. The protozoan diseases include white spot disease, hole in the head disease, itch disease, neon tetra disease and guppy killer disease. Both monogenean and digenean trematodes parasitize tropical fishes. The important crustacean parasites of tropical fish include ‘anchor worm’or ‘fish louse’ and some isopods. The keys to minimize disease outbreaks in a fish farm are maintenance of good water quality, proper nutrition and sanitation. Disease treatments should never be applied in a haphazard fashion. When needed, chemical or antibiotic treatment should be targeted at a specific problem.