Abstract: In order to obtain the optimal farming density and daily feeding amount for the tropical freshwater ornamental fish Moenkhausia costae (M.costae), a recirculating aquaculture system was used, and the effects of the different stocking densities (0.5, 1, and 1.5 individuals·L⁻¹) and the different daily feeding amounts (3%, 5%, and 7% of body weight) on the growth performance, feeding rate, and water quality indicators of M.costae were compared. The results indicated that the group with a stocking density of 0.5 individuals·L⁻¹ and a daily feeding amount of 3% of the body weight exhibited the highest weight gain rate WGR=(517.96±56.09)%, the specific growth rate SGR=(3.03±0.15)%·d⁻¹, and the lowest feed conversion ratio (FCR=1.08±0.02). Additionally, there were significant interactions between the stocking density and daily feeding amount and the FCR and feed intake (FI) of M. costae (P< 0.05). With the elevation of stocking density and feeding rate, FI, Ammonia nitrogen, and Nitrite increased. In the G9 group (stocking density of 1.5 individuals·L⁻¹ and feeding rate of 7%), the highest concentrations of Ammonia nitrogen and Nitrite were observed, which was (0.56±0.07) mg·L⁻¹ and (0.033±0.003) mg·L⁻¹, respectively. The length-weight relationship was fitted with a power function, and the equation W=0.0165L^{2.537 3}(n=100, R²=0.9873) was obtained. Under the conditions, the optimal farming density for M. costae was determined to be 0.5 individuals·L⁻¹, with a suitable daily feeding amount of 3% of the body weight. Our findings provide the valuable information for the cultivation of M.costae, which are helpful for guiding the large-scale seed production.