This study evaluated the impacts of three concentrations of dissolved CO2: Low (~5 mg L⁻1), Medium (15 mg L⁻1), High (30 mg L⁻1); on growth performance, feed efficiency and physiological condition of juvenile pikeperch reared for 105 days (15 weeks) in RAS. Fish (initial total length = 254 mm; body weight = 117 g) were stocked in triplicate tanks per treatment and fed to 1% of the total biomass. Growth indices, feed conversion ratio (FCR), specific growth rate (SGR), thermal growth coefficient (TGC), organosomatic indices, fin condition, and survival were analyzed using one-way ANOVA. At the end of the trial, fish exposed to 30 mg L⁻1 CO2 exhibited significantly lower total length, body weight, and condition factor compared to the Low group. Final body weight averaged 297 g at Low group, 250 g at Medium group, and 233 g at High group. Feed efficiency decreased markedly with increasing CO2 as FCR increased from 1.09 to 1.82, while SGR and TGC showed downward trends. Survival, organosomatic indices, fin erosion, and body weight variability were not affected. These findings demonstrate that CO2 concentrations (> 15 mg L⁻1) affect growth and feed efficiency in juvenile pikeperch, underscoring the need for strict CO2 control in RAS to optimize production and welfare. It is a condition of the CENAKVA RI financing provider to record accesses to open data. Data can be requested at the following email: dubova@frov.jcu.cz Or visit the CENAKVA RI website:https://www.frov.jcu.cz/en/faculty/faculty-parts/south-bohemian-research-centre-for-aquaculture-and-biodiversity-of-hydrocenoses-cenakva/large-research-infrastructure-cenakva