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Live feed accounts for an important share of hatcheries costs and until now no study has examined how to reduce these costs in Brazilian sardine aquaculture. Therefore, this study verified and defined the minimum rotifer density in the first feeding of Brazilian sardine larvae that results in the best growth, survival, rotifer clearance and nutritional status (Lipase activity and RNA:DNA ratio). After initial exogenous feeding, six groups in triplicate were fed at 0.1, 1, 5, 10, 15 and 20 rotifer mL−1 during eight days. No residual rotifers were observed in the low-density treatments after the second day, which reduced by half larvae survival at 0.1 rotifer mL−1 (20 ± 2%) and mean growth by more than 20% when larvae were fed below 1 rotifer mL−1 (7.7 ± 0.1 mm length). On the other hand, densities above 5 rotifer mL−1 did not increase the RNA:DNA ratio (6.02–8.68) and decreased digestion efficiency at 15 and 20 rotifer mL−1, since lipase activity dropped by 30% to 3.79 U mg−1 of protein. Therefore, based on segmented regression, the breaking point that obtained maximum growth with the minimum requirement for rotifer ranged from 2.66 to 5.79 mL−1, or 266 to 579 rotifer larvae−1 per day.
•Lower rotifer density than 1 mL−1 affected Brazilian sardine larvae development.•Higher densities than 5 mL−1 did not increase further Brazilian sardine growth.•Digestive efficiency decreased at high rotifer density.•2.66 to 5.79 rotifer mL−1 is the cost-effective range for Brazilian sardine larvae.