Effect of oxygen levels in Biofloc system on growth performance, survivability, and production of mono-sex Tilapia (Oreochromis niloticus)

Abstract

Aquaculture is increasingly recognized as a sustainable solution for meeting global protein demands. The biofloc technology (BFT) offers a promising alternative through enhanced nutrient utilization, limited water exchange, and eco-friendly practices. In the biofloc system, oxygen supply is one of the major factors that regulate the system. This study investigated how varying oxygen availability affects the growth performance of mono-sex Nile tilapia (Oreochromis niloticus) in a mini biofloc system. The experiment was conducted over 12 weeks at the Faculty of Fisheries, University of Rajshahi, using three oxygen levels: 2-4mg/L (Treatment-I: T1), 4-5mg/L (Treatment-II: T2), and 5-7mg/L (Treatment-III: T3), with three replicates per treatment. Growth performance was assessed through periodic (4-week intervals) sampling, measuring parameters such as body weight, specific growth rate (SGR), feed conversion ratio (FCR), and feed conversion efficiency (FCE). The water quality parameters were monitored with standard methods. Water quality parameters, including temperature, dissolved oxygen, ammonia, pH, and total dissolved solids (TDS), were maintained within suitable ranges for tilapia culture. All the growth performances were better in the T3 fish group. The growth performance parameters were significantly higher in the T3 fish group (final body weight: 28.15±4.25 g, weight gain: 23.56±0.71 g, SGR: 1.88±2.16) than the T1 fish group (final body weight: 28.15±4.25?g, weight gain: 23.56±0.71g, SGR: 1.88±2.16). On the other hand, the FCR was significantly lower in the T3 fish group than in the T1 fish group. These findings indicate that a high level of oxygen in T3 (5-7mg/l) in a mini biofloc system was associated with good growth performance. The results support the viability of mini biofloc systems for household and small-scale aquaculture, particularly for marginal farmers in Bangladesh.