The main aim of this work is to study the effect of using different methods of settling solids removal for recirculating aquaculture system to improve the water quality. To achieve that, the effects of water flow rates (0.05, 0.07 and 0.1 m³ min^-1), inlet diameters (32, 50 and 60 mm) and outlet diameters (32, 50 and 60 mm) for hydrocyclone, also different distance at the inlet of settling tank (4.0, 8.0 12.0 and 16.0 m from the inlet) and retention times (4.0, 6.0 and 8.0 h) for settling tank on settleable solids removed and efficiency were studied. The results indicate that, the settleable solids removed by using hydrocyclone decreased from 0.133 to 0.057, 0.102 to 0.089 and 0.106 to 0.085 kg m^-3 with increasing flow rate, inlet and outlet diameters of hydrocyclone. The settleable solids removed by using settling tank increased from 0.052 to 0.058, 0.017 to 0.041, 0.011 to 0.025 and 0.006 to 0.011 kg m^-3 after 4, 8, 12 and 16 m at the inlet tank, respectively, when the retention time increased from 4.0 to 8.0 h. The hydrocyclone efficiency in removing solids decreased from 48.5 to 33.7, 42.1 to 37.9 and 42.1 to 38.1% with increasing flow rate, inlet diameter and outlet diameter of hydrocyclone. The settling tank efficiency decreased from 27.37 to 2.70, 30.94 to 9.68 and 32.95 to 10.89 % at 4.0, 6.0 and 8.0 h of retention time, respectively, when the distance of the inlet of settling tank increased from 4.0 to 16 m.