Traditional trout farming requires large volumes of water, which increases production costs, health risks, and environmental impact. In this context, more efficient systems capable of maintaining water quality and optimizing water use are viable alternatives for the cultivation of this species. In this study, juvenile trout (32.57 ± 0.44 g) were cultivated for 42 days in a recirculation system (RAS) and in a chemoautotrophic (CB) and heterotrophic (HB) biofloc system, using 300 L tanks, with three replicates per treatment. The RAS used biological and mechanical filters, the chemoautotrophic biofloc was formed from inorganic fertilizers, and the heterotrophic biofloc was formed from the inoculum of a cultivation with bacteria established with organic fertilizers with molasses. The fish were fed commercial feed (40% CP). The temperature (14.59 ± 0.23 °C), dissolved oxygen (9.46 ± 0.16 mg L⁻¹), salinity (3.11 ± 0.08), alkalinity (174.45 ± 22.08 mg CaCO₃ L⁻¹), and total phosphorus (1.88 ± 0.64) did not differ significantly between treatments. Biofloc treatments showed higher concentrations of ammonia and nitrite compared to RAS, due to high nitrogen production and zero water renewal. However, the bacteria present managed to maintain acceptable levels for the species (Table 1). Although solids production in the CB and HB treatments was higher than the limit proposed by Becke et al. (2018), it did not interfere with the performance of the species (Table 2).
Chemoautotrophic biofloc proved viable for trout production in a closed system with zero water renewal, promoting yield and sustainability. The system maintained water quality and lower solids production compared to the heterotrophic system, which is a factor that needs to be studied for the adoption of ideal levels for the species.