This paper presents the results of cultivation of the diatom Chaetocheros gracilis (Schutt, 1985) at varying concentrations of silicates. The study describes the growth rate of C. gracilis and the length of each stage of cultivation at different concentrations of silicates. The experiment used 1 control and 3 test groups in duplicate. The nutrient medium that was used was Guillard F/2, but with different concentrations of silicates. In the control group everything was done according to a standardized protocol, while the test groups worked: in the initial stage with the normal amount of silicate and in the second stage with a double amount of silicate (S+/++), in the initial stage without silicate and in the second phase with the normal amount of silicate (S-/+), in the initial phase without silicate, and in the second phase with the double amount of silicate (S-/++). Algal concentration was measured on a daily basis, and results showed that adding a higher concentration of silicates did not cause faster growth and higher algal concentration, but contributed to greater stability of the algal culture by prolonging the stationary growth phase and not causing a sudden decrease in algallevels after the culture reached its maximum concentration. All groups showed similar maximum algal concentrations and growth in the lag phase. Groups where a double amount of silica in the GF/2 medium was added to the second stage of growing showed a longer stationary phase without a sudden decrease in algal concentrations occurring in the groups where the normal amount of silica was added to the GF/2 medium. Key