Fish feed additive used for controlling and preventing skin diseases, and preparation method thereof

The invention discloses a fish feed additive used for controlling and preventing skin diseases, and a preparation method thereof. According to the preparation method, biogas anaerobic fermentation is adopted so as to change animal waste into biogas residue with utilization value; and the fish feed additive is obtained via further processing; waste is changed into valuables, reasonable utilization of animal waste is realized, the environment is protected, and culturing cost is reduced. According to the preparation method, biogas residue obtained via fermentation is subjected to mixing granulation and particle spraying, so that nutritional ingredients are enriched, unpleasant odor is changed, palatability is improved, and feeding attraction is improved. According to the preparation method, particles obtained via granulation are subjected to grease spraying, so that floatability of the particles in water is increased, it is convenient for ingestion of fish, dissolving of the particles in water is slowed, and utilization ratio is increased. According to the preparation method, raw materials such as fructus kochiae are added, so that bacteria, fungus, and parasites on the skin surface of fish can be killed, fish immunity is improved, infected wounded surfaces and damaged skin are treated, and rehabilitation of fish with diseases is promoted.