Anabaena sp. produces harmful cyanobacterial algal blooms (CyanoHABs) worldwide that negatively impact the aquatic environment and human health. Algicidal microorganisms are effective bioactive management tools for controlling algal bloom formation. In this study, the algicidal bacterial strain KKU-NK04, which was isolated from soil collected around the Ubol Ratana Dam Reservoir in Khon Kaen, Thailand, was identified as Streptomyces lavendulae via 16S rDNA sequencing and exhibited the strongest anti-Anabaena activity among the species tested. The nutrient medium was optimized for cultivating the algicidal strain KKU-NK04, and its activity against A. lutea was assessed. Starch and peptone were identified as the most effective carbon and nitrogen sources for the strain, respectively. Experiments using the Box‒Behnken design (BBD) in response surface methodology (RSM) revealed that the removal efficiency of the algicidal strain KKU-NK04 was increased under specific culture conditions, including 20 g/L starch, 0.600 g/L peptone, and a pH of 8.50. These optimal conditions increased the removal of Anabaena sp. by 9.89% compared with that of nonoptimized media. In the internal airlift loop bioreactor with a stainless-steel sieve support (IAL-SSS bioreactor), immobilized KKU-NK04 cells exhibited a removal efficiency of 98.56% in batch conditions for Anabaena on day 3. However, under continuous conditions, the immobilized KKU-NK04 strain demonstrated a removal efficiency of 96.45%. Therefore, the algicidal activity of KKU-NK04 makes it an effective bacterium for controlling harmful algal blooms.