This study examines the effects of harvest volume and silicon (Si) concentration on the growth and biomass production of Navicula sp. A 10% harvest volume with nutrient top-up generally resulted in higher cell abundance and biomass than a 20% harvest volume, indicating that smaller harvest volumes can better sustain microalgae growth. While a higher Si concentration (0.5 g/L) usually led to increased biomass, there were instances where a lower Si concentration (0.05 g/L) resulted in higher cell abundance, suggesting a complex relationship between Si concentration and growth. This indicates that Si concentration significantly impacts growth, but its effects are not uniform, possibly depending on other environmental or metabolic factors. To optimize Navicula sp. cultivation in large-scale photobioreactors, careful management of harvest volumes and Si concentrations is crucial. Stable environmental conditions, such as a temperature range of 26.17-26.50ºC and light intensity of 3,234-3,238 lux, were found to support healthy growth, consistent with established optimal ranges. The study suggests further exploring different Si concentrations and nutrient strategies to enhance microalgae cultivation while maintaining stable environmental conditions to ensure successful biomass production.