Effect of no carbohydrate addition on water quality, growth performance and microbial community in water-reusing biofloc systems for tilapia production under high-density cultivation

Abstract

A 56‐day experiment was conducted to investigate the effect of no carbohydrate addition applied to control water quality in water‐reusing biofloc systems for tilapia (GIFT Oreochromis niloticus) cultivation. Reusing water‐contained flocs was initially inoculated into six 300 L indoor tanks. Thirty fish (average individual weight 99.62 ± 7.34 g) were stocked in each tank. Glucose was extra added into three tanks (GLU‐tanks) according to biofloc technology, while other tanks were no carbohydrate added (NCA‐tanks). Concentrations of total ammonia nitrogen in GLU‐tanks and NCA‐tanks were fairly consistent and below 4.74 ± 0.35 mg/L. Nitrite concentrations in NCA‐tanks were significantly lower than GLU‐tanks, which were below 0.59 ± 0.10 mg/L during the later culture period. NCA‐tanks achieved a low relative abundance of denitrifiers and high concentrations of nitrate. Soluble reactive phosphorous in NCA‐tanks was consistently increased, which was decreased to a low level in GLU‐tanks. However, growth parameters in NCA‐tanks were similar to GLU‐tanks (p > .05) and reach a high finial density of 24.32 ± 1.04 kg/m3. Cetobacterium sp. was the first‐dominant bacterial genus in all tanks, which was a commonly indigenous bacterium in the intestinal tract of freshwater fish. The results demonstrate the feasibility of no carbohydrate addition in water‐reusing biofloc systems for tilapia.

Growth, water quality and oxidative stress of Nile tilapiaOreochromis niloticus(L.) in biofloc technology system at different pH

“…The low or zero water exchange characteristic of the BFT systems is associated with the correct management of water quality, providing conditions for establishment and growth of nitrifying bacteria (Avnimelech, 2012). This may favour the accumulation of nutrients, such as N and P (Liu, Luo et al, 2018). In the present study, At high stocking densities, the TSS and their control are a limiting factor, and the removal of excessive bioflocs is necessary (Ray, Lewis, Browdy, & Leffler, 2010).…”

“…The fertilization with C organic only for TAN >1.0 mg/L is favourable to initial heterotrophic growth, and after the TAN consumption, no more fertilizations occur. Thus, throughout the production cycle, the C:N ratio decreases, which is favourable to autotrophic growth (Liu, Luo et al, ). In this present study, this strategy proved to be efficient for nitrogenous cycling.…”

“…The low or zero water exchange characteristic of the BFT systems is associated with the correct management of water quality, providing conditions for establishment and growth of nitrifying bacteria (Avnimelech, ). This may favour the accumulation of nutrients, such as N and P (Liu, Luo et al, ). In the present study, the NO 3 − ‐N concentrations reached high levels because the intense nitrifying activity, but according with Monsees, Klatt, Kloas, and Wuertz (), values below 500 mg/L ensure the optimum growth and health to Nile tilapia.…”

“…Similarly, Luo et al (2014) demonstrate low concentrations of phosphate on BFT compared to RAS, indicating PO 4 −-P cycling by microorganisms is present in bioflocs. Ray and Lotz (2014) also found low concentration of PO 4 −-P, which they attributed to absorption by heterotrophic bacteria, as demonstrate for Longnecker, Lomas, and Van Mooy (2010) andLiu, Luo et al (2018). The monitoring of NO 3 −-N and PO 4 −-P water levels in aquaculture systems is fundamental, because could be indicators for reuse as well as for correct discharge as effluent.…”

“…Different strategies for organic fertilization have been proposed for biofloc formation during Nile tilapia production, such as the utilization of different C:N ratios (Liu, Zhu, Liu, & Ye, ; Pérez‐Fuentes, Hernándes‐Vergara, Pérez‐Rostro, & Fogel, ) and carbon sources (Ekasari, Crab, & Verstraete, ). Thus, it has been demonstrated that, in biofloc systems, there is nitrification, especially when C:N ratio is reduced (Liu, Luo et al, ).…”