Understanding the distinct behavioral and physical dietary preferences of shrimp is crucial for establishing the feeding needs of these animals, given their unique and slow continuous feeding behavior. Pellet size could impact the physical attributes of the diet, feeding behavior, and biological performance. The breakdown of diet particles into smaller pieces, either due to pellet breakdown after immersion or shrimp manipulation, leads to direct nutrient losses, generating fines that may contribute to poor water quality and increased operational costs. Hence, it is crucial to identify the optimal diet size to improve both the physical performance of the pellet and the biological performance of the animal. The objective of this study was to evaluate the response of L. vannamei fed different sized feed in a biofloc system. The experiment was conducted in an outdoor biofloc recirculating aquaculture system consisting of 20, 800L culture tanks. The shrimp were stocked (1.7 g) at 44 shrimp/m3 and raised for 8-weeks. Different sized feed each with 35% CP (1.5 mm , 2.0 mm , and 2.5 mm) were fed for 8-weeks as three treatments. During the first four weeks, a 1.5 mm feed was fed and then switched to 2.5 mm feed for the remaining four weeks as the fourth treatment. This resulted in a total of four treatments with five replicates each. Significant differences in growth and feed conversion ratio (FCR) between treatments were observed. The highest biomass (661.1g) and mean weight (20.0 g) were recorded in shrimp fed 1.5mm feed for first four weeks and 2.5mm feed for the last four weeks. An increase in the biomass, mean weight, and weight gain were observed with an increase in feed size. FCR decreased with the increase in feed size. The findings from this study indicate that offering shrimp an adequately sized feed tailored to their specific growth stages contributes to maximizing their growth potential. In conclusion, the research underscores the importance of fine-tuning diet size to the specific growth stages within a bioflo c system to improve both the physical and biological performance of L. vannamei.