Background: High stocking density and intensive feeding in aquaculture systems lead to the accumulation of organic waste, which results in an increase in ammonia, nitrite, and nitrite concentrations in culture media. Biofloc is a potential technology to overcome this problem. The starter is a crucial carbon source for bacteria in the formation of biofloc. The objective of the present study aimed to explore the best starter of biofloc in a red tilapia Oreochromis niloticus culture system.

Methods: A completely randomized design with four levels of treatment was used in this study. The tested starter was (A) control treatment, biofloc without starter,(B) biofloc with molasses starter,(C) biofloc with tapioca starter, and (D) biofloc with sucrose starter. The floc was cultured in 100-L tanks with a salinity of 17 ppt. The tanks were stocked with O. niloticus with a size of 3.71±0.11 cm at a stocking density of 30 fish per tank. The fish were fed on a commercial diet two times a day at satiation for 40 days. The ammonia, nitrite, and nitrite concentrations were measured for an interval of 8 days.

Results: The study showed that the NH 3-N range was 0.02–0.07 mg L− 1 (mean, 0.03±0.02 mg L− 1), NO 2-N range was 0.20–0.43 mg L− 1 (mean, 0.25±0.12 mg L− 1), and NO 3-N range was 0.90–3.20 mg L− 1 (mean, 1.42±1.19 mg L− 1).

Conclusion: Among the starters tested, molasses was found to be the best for biofloc in tilapia culture.