Impact of alkalinity treatments on biofloc dynamics and growth performance in Penaeus vannamei shrimp culture

Biofloc technology is eco-friendly due to its minimal water exchange in aquaculture. However, it may lower alkalinity in pond water due to organic acids produced during biofloc incubation. This study assessed the effects of three alkalinity treatments—CaCO₃ (C), MgCO₃ (M), and their combination (MC)—on water quality, biofloc incubation, and Penaeus vannamei shrimp growth. Treatments C and M were dosed at 20 mg L⁻¹, while MC combined 10 mg L⁻¹ of each compound. Shrimp larvae with an initial weight of 0.044 ± 0.01 g were cultured for 52 days. Treatment MC significantly increased floc densities compared to the control, although differences among treatments were not significant. Ammonium levels in M and MC were lower than the control on days 10, 25, and 30, while nitrate levels in M and MC were higher. Total hardness was higher in all treatments compared to the control but did not differ significantly among treatments. Shrimp in treatment C showed significantly higher weight gains (0.21 ± 0.03 g) compared to treatments M and MC (0.19 ± 0.003 and 0.20 ± 0.02 g, respectively) and better food conversion ratios (1.27 ± 0.2) compared to treatment M (1.42 ± 0.02). Meanwhile, survival rates did not vary significantly between treatments. It indicates that the addition of C is better for shrimp growth than with M and MC. Overall, M and MC treatments enhanced water quality and biofloc levels, while C was most effective for shrimp growth.