An 8-week experiment was conducted to investigate the effects of biofloc technology (BFT) on the growth,
digestive activity, hematology, and immune response of genetically improved farmed tilapia (GIFT) in light-
limited and zero-water exchange culture tanks. The experiment consisted of one BFT treatment and a control
group with water exchange. Glucose was added to the BFT treatment to establish a carbon/nitrogen (C/N)
ratio of 15. The stocking density was 3 kg m−3
in each 500-L indoor tank. Nitrite and nitrate concentrations
were significantly lower in the BFT treatment than in the control (P b 0.05). Fish survival was 100% at harvest.
BFT significantly increased fish specific growth rate and net yield. Compared with the control group, the
individual fish weight, weight gain and protein efficiency ratio of fish in the BFT treatment were 12.54%, 9.46%,
and 22.2% higher, respectively, whereas the feed conversion rate was 17.5% lower. The crude protein, crude
lipid, and ash contents of the biofloc were 41.13%, 1.03%, and 6.07%, respectively, while the crude lipid content
of BFT fish exhibited an increasing trend. Significantly higher intestine amylase and liver lipase activities of fish
were found in the BFT treatment. There was no significant difference in hematology analysis (in terms of
white blood cell and red blood cell counts, hemoglobin and hematocrit levels), serum total protein content or
total superoxide dismutase activity of fish between the two groups (P N 0.05), but the serum glutathione
peroxidase and lysozyme activities were considerably higher in the BFT treatment than in the control fish
(P b 0.05). The results of this study indicate that BFT can improve the growth, digestive enzyme activities, and
immune response of GIFT.