Impact of Substrate-assisted Biofloc Technology with Different Stocking Densities on Water Quality and Microbial Community of Penaeus vannamei Nursery Rearing

Abstract

The present study evaluates the effect of inclusion of substrate on water quality and microbial community of biofloc-based nursery-rearing system for Penaeus vannamei with different stocking densities 30 days experiment was carried out in 100 L capacity HDPE tanks. The experiment consisted of two factors as biofloc without substrate (BT) and biofloc with substrate (BST) with four stocking density treatments (2000, 4000, 6000, and 8000 nos. m-3) with three replicates. The substrate a bamboo mat, was introduced, covering 100% total surface area of the tank. Water quality parameters, including pH and dissolved oxygen levels, were significantly influenced by substrate addition with varying stocking density. The biofloc system with bamboo mat (BST) exhibited lower TAN, Nitrite‐N, Nitrate‐N, Biofloc Volume and total suspended solids (TSS) compared to without substrate treatments, and its concentration increases with an increase in stocking density. The total bacterial count (TBC) was consistently higher in substrate treatments (1.64 to 2.26 × 10⁵ CFU mL⁻¹) compared to non-substrate treatments (0.88 to 1.53 × 10⁵ CFU mL⁻¹). Also, substrate availability markedly enhanced Bacillus proliferation and relatively stable Vibrio population (2.18 to 2.31 × 10² CFU mL⁻¹) suggests that the biofloc system effectively maintained microbial equilibrium. The incorporation of substrates enhanced the microbial community associated with biofilms, contributing to improved nitrogen cycling.