The present study aimed to investigate the effect of flumequine on growth of Nile tilapia when used as prophylactic and chemotherapeutic agent in both glass tanks and concrete ponds as well as its cytogenetic effect, the present study was carried out as two experiments. In the first experiment, fish were reared in glass tanks, using fingerlings of Nile tilapia (all male sex reversal). Fish were grouped into four groups (in two replication), group 1 served as control, fish in groups 2 were administered therapeutic dose 12 mg/kg of body weight/day, as medicated feed for successive 5 days, groups 3 were administered subtherapeutic dose 10 mg/kg of body weight/day during the experimental period (9 weeks) and groups 4 were administered 6 mg / kg of body weight/day during the experimental period. Growth parameters, feed conversion ratio, protein efficiency ratio, and survival rate were recorded. Flumequine residues in tissue were determined as well as cytogenetic studies were performed. The second experiment was carried out in a private fish farm, whereas fish were reared in concrete ponds. One-month age monosex fry were used. Fry were divided into two groups, the first group (control) was fed control diet (free from flumequine). The second group was fed medicated diet, flumequine was added at dose of 10-mg/kg of body weight/day during incubation period, then the two groups were fed control basal ration until the end of experiment. The obtained results indicated that flumequine in dose of 10 mg/kg of body weight/day caused a significant increase in the body weight, weight gain and protein efficiency ratio, in addition to improvement in feed conversion ratio, compared to control fish group reared in glass tanks (experiment I). Survival rate found to be 89.30, 85.72, 100 and 92.86% for fish groups fed the experimental diets 1, 2, 3 and 4, respectively. Flumequine in dose of 10 mg/kg of body weight/day caused significant increase in chromosomal aberration, compared with control group. Flumequine residues were detected in fish tissue until 10 and 20 days after last feeding in group administered 10 mg/kg of body weight/day, whereas fish administered 6 mg/ kg of body weight/day, flumequine not detected after 10 days of last feeding. Addition of fiumequine to fish diets at dose of 10 mg/kg of body weight/day in concrete ponds (Expeiment II) caused significant decrease in body weight at the end of incubation period, this decrease became non significant at the end of the experiment. From the obtained results it could be concluded that, flumequine in dose of 10 mg/kg of body weight/day caused significant increase in growth rate, and improved feed conversion ratio as well as increased in survival rate in aquaria system. However, in fish farm flumequine caused inhibition of growth rate. Subsequently, flumequine in dose of 10 mg/kg of body weight/day can be used as prophylactic dose in aquaria system for improvement of growth and decrease mortality especially during incubation period.