When buying fry, we should first carefully investigate whether the parent fish used by the fry breeding unit meets the national breeding standards, and the fry produced by the small and mature parent fish bred by inbreeding are all bad fry. The quality of fry can be identified from the following aspects. 1, through naked eye observation, more than 95% of fry should conform to the development stage of fry concept. 2. Swim in groups with lively movements. When the water is stirred slightly in the container, more than 95% of the fry have water-holding ability. 3. Countable indicators: the deformity rate of herring should be less than 5%, other fry should be less than 3%, and the injury rate should be less than 1%. 4, more than 95% of the fry, black carp should reach 0.8, grass carp should reach 0.7, silver carp should reach 0.8, silver carp should reach 0.9, and bream should reach 0.5 or more.