Evaluation of long-term operational and production performance of biofloc technology (BFT) system within various particle size.

Biofloc technology (BFT) is a promising technique, but there has been ongoing debate between biofloc's properties and particle size. This study investigated the relationship between long-term particle size variation and the production performance of BFT aquaculture systems. External shearing force introduction could keep bioflocs at a smaller size level chronically, and 97% of smaller bioflocs were below 181.97 μm which was obviously lower than the normal size group (Control). No significant difference in the daily water treatment capacity for bioflocs within different particle size was detected (p > 0.05), but the activity of Soil-Dehydrogenase (S-DHA), Ammonia Monooxygenase (AMO), Hydroxylamine Oxidase (HAO) and Nitrite Oxidase (NOR) were all higher in smaller bioflocs. Smaller bioflocs were better enriched heavy metal elements and less damage to the gill lamellae was also detected in smaller size group. The survival rate and final mean weight of tilapia (Oreochromis niloticus) cultured in the BFT system based on smaller size bioflocs were significantly higher than the control (p < 0.05). The microbial compositions of varying particle sizes bioflocs demonstrated remarkable distinctions, and higher abundance of particle-attached bacteria (e.g., Flavobacteriaceae, Rhodobacteraceae) was detected in normal size bioflocs. Overall, this study comprehensively evaluated the long-term application of various particle size bioflocs and provided a practical basis for the sustainable BFT development. • External shearing force introduction can maintain bioflocs in the smaller particle size. • The activity of S-DHA, AMO, HAO and NOR are higher in bioflocs with smaller size. • Smaller bioflocs provide relatively better growth performance of tilapia (Oreochromis niloticus). • The microbial composition of smaller-sized bioflocs becomes more diverse as time progresses. [ABSTRACT FROM AUTHOR]