Experimental design.
One hundred O. niloticuswere distributed into five glass aquaria and acclimatized for the experimental conditions for 15 days prior to the start. During that period fish were adapted on feeding of control diet (without any additives). Water was changed every week to maintain good water quality. Water temperature and pH were adjusted at 20-250C and 7.4 respectively during the experimental period. The experimental design is to be seen in table (1).