Healthy unsexed O. niloticus fingerlings (2.7±1g) were collected from the Federal University of
Technology Alcure fish farm and acclimated for two weeks and fed with a 40% protein diet prior to
commencement of toxicity tests. They were later stocked into 28 rectangular glass tanks
(75x40x40cm) filled with 45 litres of spring water (pH, 7.2+0.1; temperature, 27.5°C; total'
hardness and alkalinity, 168-213mg/1) and starved for two days. Fish were randomly distributed at
10 fish/tank in duplicated treatments