Biofloc is a new emergence technology in aquaculture industry that relies on the carbon and nitrogen ratio to remove the toxic nitrogenous waste from aquaculture water. This technology requires start-up period to achieve well-functioning system in maintaining the good water quality for sustainable aquaculture system. During this stage, ammonia fluctuation typically occurs due to bacteria development. This study aimed to evaluate the effect of different carbon to nitrogen (C/N) ratios, carbon sources, and aeration flow rates on the ammonia fluctuations during start-up period of biofloc formation using bioflocculant-producing bacteria, Bacillus infantis as inoculum. This experimental study was conducted in 25 L synthetic aquaculture water that initially contained ± 5 mg/L to study the ammonia trends in varied C/N ratio (5, 10, 15, 20), carbon sources (molasses, rice bran, glucose, and sucrose), and flow rates (< 2.5, 2.5–5.0, 5.0–7.5 L/min). The dynamic changes of ammonia and other water quality parameters were observed at every 2-h interval, up to 10 h during the experimental period. In various carbon source experiment, sucrose’s ammonia level showed significant changes and was reduced to 4.47 mg/L during the early stages. However, in different C/N ratios and flow rates experiment, the ammonia shows fluctuated result and gives insignificant changes to ammonia reading. Both experiments recorded the best ammonia trend at C/N 20 and flow rates of 5.0–7.5 L/min. Generally, within the first 10 h of the investigation, the fluctuated ammonia trend was caused by the lag phase of heterotrophic microorganisms in the BFT system. Thus, the alternative to overcome this issue is needed to rapidly reduce the effect of start-up stages and remove ammonia.
