Hello! In fact, it's not just the larvae of pearl grouper in seawater. I have raised many kinds of fry, and this problem basically exists, such as the fry of PARALICHTHYS olivaceus, sea bass, puffer fish, tiger spot and freshwater rainbow trout. In general, the number of blackbody seedlings is small, and the infectivity is not strong or non-infectious, and only a few seedlings occasionally have blackbody. We believe that this should not be an infectious disease in itself, but a physical immunity problem of individual seedlings in the process of seedling raising, or a lack of food or poor function of individual seedlings in the seedling opening stage, which should be a normal weak seedling elimination. If there is a large area of blackbody problem, it needs to be examined by a microscope to determine whether there are parasitic diseases or bacterial diseases.

Regarding the problems that should be paid attention to in seedling raising, we must first ensure that the bait is sufficient, feed it as early as possible every day, and try to feed it before the sun comes out to prevent the seedlings from killing each other; Secondly, pay attention to stocking density and try to maintain a reasonable stocking density; Thirdly, it is necessary to arrange the time of seedling separation reasonably and separate the fry of different specifications to prevent the phenomenon of big fish eat small fish; Fourth, if the seedlings are raised in a cement pond instead of a pond, the water should be changed as much as possible to keep the feces and residual bait in the cement pond discharged in time; Fifth, fry should prevent diseases regularly.