The rapid expansion of the aquaculture industry is accompanied by high organic and nutrient loadings from formulated feeds. This leads to water deterioration and pathogenic microorganisms. Natural biota (e.g., bacteria, phytoplankton, zooplankton, and zoobenthos) in ponds form important parts of cultured aquatic animals’ diets. They contain essential proteins, lipids, carbohydrates, amino acids, and fatty acids and are considered promising supplementary nutrition sources for cultured aquatic animals. Particularly, they are available to aquatic animals throughout the day, and an adequate supply of them as starter foods during the larvae stage ensures high survival. Since formulated feeds constitute more than 50% of aquaculture production costs, optimizing the utilization of natural biota and reducing dietary nutrient input without compromising animals’ growth should be a priority to improve the economic success and sustainability of aquaculture. From this scenario, the present review offers an updated view of the natural biota category in aquaculture systems, their nutritional components, and their contributions to the growth of cultured aquatic animals. Taken together, this review emphasizes the significant roles of natural biota playing in the growth of aquatic animals and encourages maximizing utilization of natural biota to improve feed conversion efficiency and aquaculture sustainability.

Off-seasonal water level regulations disrupt the biological traits and phenological rhythms of native fish species, yet their impacts on interspecific trophic interactions remain understudied. This study employed stable isotope analysis to assess the trophic dynamics of three fish species (Parabramis pekinensis, Carassius auratus, and Toxabramis swinhonis) across different water periods in Hongze Lake. The findings revealed that all three species occupied similar mid-level trophic positions, with no significant difference among water periods (p > 0.05). During high-water periods, P. pekinensis and T. swinhonis exploited broader niches, while C. auratus relied on a narrower diet. In contrast, during low-water periods, C. auratus expanded its niche, while P. pekinensis and T. swinhonis reduced their isotopic niche widths. Niche overlap analysis showed minimal trophic overlap among the three species during high-water periods, with increased overlap during low-water periods, except for the highest overlap between C. auratus and T. swinhonis during mid-water periods. This variation in niche overlap aligns with shifts in dietary reliance, as POM was the predominant dietary component for all three species, but its contribution varied significantly across different water periods. These findings indicated that adaptive trophic niche facilitated the coexistence of these fish species, while off-seasonal water level regulation may intensify interspecific competition. These insights are essential for refining water management policies and developing sustainable fishery management strategies of Hongze Lake and other water-level-regulated systems.