In present study, the changes in the biochemical compositions of Na-alginate microcapsules with diameters between 80μ-900 μ were determined. To achive this purpose, six groups(80-200μ; 200-250μ; 250-355μ; 355-500μ; 500-900μ; >900μ) of microcapsules were analyzed. The significant differences between dry matter, ash and lipid amounts of microcapsules were found (P900μ) and 21.85±0.85% (355-500μ), respectively. Also, the differences be-tween protein amounts of all microcapsule groups were statistically significant (P0.05). Re-sults showed that the highest protein amount was 66.24±0.05 % (80-200μ). Our study revealed that low survival and growth rates in marine fish larae may be related to the result of the changes in biochemical compositions of microcapsules used in the feeding of larvae. In conclu-sion, the changes in the biochemical compositions of microcapsules produced in the different size classes with other manufacturing methods to sustainable aquaculture should be investi-gated in future studies.