Abstract: Two hundred rocky water prawns, Caridina africana were exposed to different concentrations of 0.0g/l, 0.10g/l, 0.15g/l, 0.20g/l and 0.25g/l) of Copper sulphate and Aldrin solution. The median, lethal concentration (Lc50) for 96hours were determined and the behavioral pattern also. The 96-h Lc50 values were 0.15g/l for Copper Sulphate and 0.17g/l for aldrin solution. The pesticide at varying concentration has significant effect on loss of reflex, increase hyperactivity, discoloration and hypereticulation. Logit and probit analysis showed no significant difference (<0.05) between the two toxicants.