Mass production technique of nanoscale TiO₂ particle-embedded expanded polystyrene (EPS) balls with temperature-controlled melting method was developed, and the photocatalytic activity of TiO₂-embedded EPS (TiEPS) balls to suppress the excessive growth of Microcystis aeruginosa (M. aeruginosa) cultured from both indoor and outdoor experiments was verified under ultraviolet and solar light irradiation, respectively. According to the experimental results, the growth inhibition of M. aeruginosa was evidently observed by applying TiEPS balls, and increased proportionally with the surface area coverage of TiEPS balls. Based on the comparison of both specific growth rate (μ) and first-order degradation rate (k), the experimental cases using TiEPS balls with surface area coverage of 100% suppressed more significantly the growth of M. aeruginosa cultured from both indoor and outdoor experiments during the initial period of the experiment. However, through the whole experiment, both μ and k values between experimental cases using TiEPS balls and EPS balls with surface area coverage of 100% were not statistically different (p > 0.05). These results indicated that the photocatalytic degradation effect was dominant during the initial period of application, and the irradiation shading became dominant with the elapsed time. Therefore, the growth of M. aeruginosa can be suppressed due to both synergistic and combinational effects of photocatalytic degradation and irradiation shading under natural solar light. Based on the aforementioned results, self-floating TiEPS balls produced from this simple and cost-effective mass production technique can be readily applied to inhibit the excessive growth of harmful algae in the stagnant water body.