RESUMEN
Reared Nile catfish, Clarias lazera [C. lazera], in a rice farm infested with rice scum and treated by copper sulphate [Cu So4] in concentration of 2.5 mg/l water slowed different biochemical deviations in their red blood cells [haemolysate]. This haemolysate presented significant decreases [p < 0.05, P < 0.01 and P < 0.001] in mineral levels of calcium [Ca], inorganic phosphorus [P] und potassium [K] at 2[nd], 4[th], 6[th], 8[th] .and 10[th] days of exposure. Sodium [Na] levels were significantly increased at [P < 0.05 and P < 0.01] and levels of total protein and total lipids monitored no significant changes in haemolysate after the same periods of exposure to Cu So4. Plasma of the same fishes showed significant elevations [p < 0.05, P < 0.01 and P < 0.001] in levels of [Ca], [P] and [Na], while [K] levels had significant declines [P < 0.01] at the same intervals of sampling. K/Na ratios in haemolysate and plasma of C. lazera were markedly decreased allover the period of treatment