Aquaculture Disinfectants: Types and Uses Disinfection is a common disease management tool for aquaculture sector. It can be both a routine bio-security practice to prevent specific diseases or a routine sanitation process to reduce overall occurrence of diseases that may lower farm productivity. The nature and mode of disinfection greatly varies with the specific reason that leads to disinfection practices. The most commonly practiced approach is chemical treatment in specified doses and for sufficient retention periods to destroy pathogenic organisms that would otherwise access the water systems repetitively. In aquaculture systems, the threat of cross contamination is prevalent between fauna in the same tank as well as between water holdings, both in fish and crustacean farming. In addition, use of disinfectants is not possible in open systems owing to environmental impacts of chemicals in natural waters and in case of seawater; there is risk of residual oxidant byproducts due to chemical reactions with salts in water. Thus disinfectants can be applied safely and most conveniently only to hatcheries and incubation tanks. Since most aquatic species are highly sensitive to toxic chemicals and the disposal of such waters threatens to contaminate natural water bodies, it is highly needed that a “safe” product be used for disinfection. The term “safe” implies to toxicity tolerance by farm as well as wild aquatic organisms. Thus only a few chemicals can truly adhere to the properties of ideal aquaculture disinfectants in real practice. Some disinfectants are effective against a large range of microorganisms: bacteria, viruses, fungi and parasites. In addition some chemicals are selective biocides to certain strains of exotic eutrophic microalgae. While some disinfectants can work on a short term before the microbes grow resistant to them. Thus the choice of disinfectant and methods of disinfection should be based on the spectrum and ease of application as well. Requisites of an ideal Disinfectant are summarized herein:
Should have a wide spectrum antimicrobial activity Should not be irritating to aquatic organisms or humans Should have minimal toxicity to non target organisms Should have high penetrability Should be active in presence of Pus and Necrotic Tissue Should be non-interfering with normal immunity of fishes Should be cost friendly Should be non corrosive and non staining Should be highly stable Should be biodegradable with nil/minimum bioaccumulation potential
Disinfectants can be classified based on their mode of activity as: 1. Oxidizing Agents 2. Reducing agents