Optimization of light utilization and dissolved gases (DO/CO₂) is essential for enhancing volumetric productivities in microalgae production processes operating at high cell densities. This research explores the interplay between irradiance and gas control on growth dynamics and nutrient uptake of the thermo-acidophilic microalgae species Galdieria sulphuraria. Four scenarios were analyzed with respect to two flat-panel photobioreactor systems operating as biological replicates: irradiance at 100 and 250 µmol photons m⁻² s⁻¹ in open-loop and closed-loop gas modes. All experiments were carried out continuously with the inoculum concentration set at 1.5 g/L through 24-hour sampling intervals for analysis of biomass dry weight, optical density, and nitrogen content.