<p>We examined the effects of different stocking densities on the growth and survival rate of ide (<i>Leuciscus idus)</i> and barbel (<i>Barbus barbus</i>) larvae. The fish were reared for 21 days in RAS. Ide larvae were stocked at four densities (25, 50, 75, and 100 larvae l⁻¹), while for barbel, the effects of two different stocking densities (50, 100 larvae l⁻¹) were examined. At the beginning of the experiments, 9 days post-hatch, total length, and body weight of ide larvae were 10.36 ± 0.36 mm and 2.39 ± 0.51 mg, respectively. The same parameters for the barbel were 13.06 ± 0.92 mm and 10.98 ± 1.77 mg. Initially, the fish were fed with live <i>Artemia</i> nauplii, and then they received dry food. The mean final length and weight of ide larvae (30 days post-hatch) across all treatments were 15.12 ± 1.76 mm and 26.85 ± 7.58 mg, respectively. The average survival rate was 82.7 ± 6.25%. Increasing stocking density did not affect adversely the examined indicators. The mean final weight of barbel larvae across all treatments was 629.3 ± 161.6 mg without a significant difference between the two groups. Significantly higher final length was measured in the 50 larvae l⁻¹ group (20.04 ± 2.08 mm) compared to that of the 100 larvae l⁻¹ group (18.83 ± 2.46 mm). High survival rates were recorded for both groups (above 90%) without differences. Pre-nursing of ide and barbel larvae in RAS resulted in perfectly developed offspring with extremely low mortality.</p>