Effects of Nannochloropsis oculata and Isochrysis galbana microalgae added in biofloc system on body composition and sensory evaluation of fillets in Nile tilapia, Oreochromis niloticus

Biofloc technology is a technique to maintain water quality by absorbing water nitrogen and converting it into the microbial protein. The purpose of this study was to investigate the effects of adding Nannochloropsis oculata and Isochrysis galbana on biochemical composition of biofloc and Nile tilapia (Oreochromis niloticus) fillet. This study was carried out using 5 treatments including control (T1), biofloc group (T2), treatments containing biofloc and N. oculata (T3), biofloc and I. galbana (T4), and biofloc and combination of both algae (T5) on Nile tilapia with a density of 15 fish per tank (with water intake volume of 150 liters) and in the system without water exchange in a period of 60 days. According to the results, the highest values of fish fillet fat were obtained in the treatments containing biofloc (p<0.05). No significant difference was observed in the dry weight and carcass protein values among the treatments containing biofloc (p>0.05); however, significantly highest compared to the control (p<0.05). The amount of ash did not show a significant difference among experimental treatments (p>0.05). Also, the highest amount of carbohydrates was observed in the control group (p<0.05). Based on organoleptic properties of tilapia fillets raised in the biofloc system and control treatment, fillet color, taste, texture, chew ability, and general acceptability did not exhibit any significant differences among different treatments (p>0.05). Using 75% of the feeding required for tilapia in the biofloc system caused an elevation in body protein compared to the control treatment. In addition, the amount of fat also upraised due to the employment of this system. Using single-celled algae resulted in an increase in the amount of biofloc and an effect on the composition of Nile tilapia fish fillets.