Immunostimulants are valuable for the control of fish diseases and may be useful in fish culture. Microbial pathogens are one of the main problems in the rearing of larvae. It is therefore important to develop methods for establishing microbial control at all stages of the cultivation progress. One possibility is immunostimulation, which includes methods of enhancing the capacities of the specific and nonspecific immune systems. There are many experiments on nonspecific immunostimulation of fish that suggest that the method has considerable potential for reducing losses in aquaculture, both during larval and on-growing stages. So, on one hand, we can say that use of immunostimulation in larviculture is possible. On the other hand, due to the small size and fragility of larvae the development of methods to administer the stimulant, and the adaptation of methods for detecting the response of the immune system is full of challenges. The aim of the paper is to evaluate the status and the potential for immunostimulation as an element in the strategy for solving microbial problems in larviculture. The focus will be on fish, but the ideas are also applicable to other groups of organisms relevant to aquaculture.