This study was conducted to determine the effect of different stocking densities on growth rate of Asian swamp eel (Monopterus albus), growth of watercress (Nasturtium officinale) in a floating-draft aquaponic recirculating system. Two factorial experiment designs consist of three different swamp eel (16.67 ± 3.48 g/individual) densities of 100, 180 and 260 individuals/m2 (8.4, 15.0 and 21.7 kg/m3, respectively) integrated with hydroponic trough of watercress (SEW) or without watercress (swamp eel only, SE). Watercress seeds were put into styrofoam, floating rack (80 heads/m2). Swamp eels were fed 2 times per day with commercial pellet (42% protein). The experiment was run for 65 days with two cycles of watercress. Statistical analysis by Two-way ANOVA showed that there is no significant difference (P > .05) in growth performance of swamp eel at different stocking densities between the SEW and SE systems. However, statistical analysis by One way ANOVA showed that there is a significant difference (P < .05) on weight gain (WG) and daily weight gain of animals among the SEW treatments. The highest WG was 32.78 ± 2.09 g/ind. and 41.71 ± 9.05 g/ind. for treatment of 180 inds./m2 at the SEW and SE, respectively. The average survival rate of animal in all treatments was above 80% and was not significant difference among the treatments. The lowest FCR (2.15 ± 0.94) were found in treatment 180 inds./m2 of the SEW. Production of watercress was low in all treatments, the highest biomass (507.81 ± 91.01 g/m2) was recorded for treatment 180 inds./m2 of the SEW. Nutrient accumulation was relatively high at higher stocking densities of swamp eel and was higher in the SE system compared to the SEW system. Total ammonia nitrogen (TAN) concentrations in the SE treatments were ranging from 2.61 ± 1.81 mg/L (120 ind./m2) to 5.77 ± 3.19 mg/L (260 ind./m2). Whereas, the TAN levels in the SEW treatments were only ranging from 1.94 ± 1.44 to 5.35 ± 0.36 mg/L and even lower in hydroponic trough (1.3–3.15 mg/L). Similarly, nitrate‑nitrogen level was high in the SE treatments (1.43 ± 1.36–2.36 ± 1.43 mg/L) and lower in the SEW treatments (0.89 ± 1.36–1.42 ± 1.34 mg/L). Generally, swamp eel farming combined with hydroponic trough was feasible in handling water quality and required little water change in contrast to SE treatments which required as much as 1 water change a day. This study found that the stocking density of 180 inds./m2 seems to be the most effective density for growth, survival of swamp eel as well as nutrient accumulation in the SEW. The results of this study provide an important information as to how aquaculture of swamp eel may be expanded in the Mekong Delta without destroying the environment by releasing nutrient rich effluent from growing chambers.