Three hundred and sixty (360) juveniles of Clarias gariepinus were collected from Luis Fish Farm Warri, Delta State and transported to the Departmental Laboratory of Fisheries and Aquaculture, Ebonyi State University Abakaliki (latitude 6⁰, 20\' 49\'\'N, longitude 8⁰ 06\' 11\'\'E), Nigeria. The experimental fish were exposed to 6 treatment concentrations (20, 10, 5, 2.5, 1.25 and 0.00) ml/l of WSF of BLCO in triplicate replications of 60 fish per treatment for 10 weeks. Mean cell count of red blood cell (RBC) reduced significantly (P<0.05) from 2.09±0.06 x 10⁶ /mm³ in the control group to 1.4971±0.06x10⁶ /mm³ in the highest concentration exposed group (20ml/L). Similarly, significant reduction in packed cell volume (PCV) and haemoglobin content of RBC resulted to anaemic conditions in exposed fish. PCV decreased from 24.33±0.26% to 16.50±0.89% while haemoglobin decreased to 7.73±0.29g/dl from 12.05±0.11g/dl. Total white blood cell (WBC) count suffered significant reduction than control and in the amount of its lymphocytes but increased significantly than control in the number of neutrophils. WBC reduced from 51.44±0.47x10³ /mm³ to 43.48±1.09x10³ /mm³ , and lymphocytes from 91.55±2.24% to 78.0±0.5% while neutrophil increased to 11.52±1.3% from 3.58±0.27%. Mean corpuscular volume (MCV), MCH and mean corpuscular haemoglobin concentration (MCHC) did not differ significantly (P>0.05) with control group.