The Nutrient Film Technique (NFT) in aquaponics is a closed aquaculture system favored by Indonesian aquaculturists due to its environmental friendliness and can be applied on a small scale. Climbing perch (Anabas testudineus) has the potential to be cultured in this system as small-scale livestock. This research aims to determine the performance of the NFT aquaponics system of Anabas testudineus and Brassica chinensis with different stock densities. A completely randomized design within four stock density treatments and five replications was applied to this study. The results showed that the specific growth rate, survival rate, and feed conversion rate (FCR) of A. testudineus differed significantly across treatments (p < 0.05). The best performance of specific growth rate (1.96 ± 0.15%), FCR (1.31 ± 0.13), and survival rate (88 ± 4.69%) were shown in the second treatment (50 fish/tank). On the other hand, the fourth treatment (100 fish/tank) yielded the tallest B. chinensis at 20.7 ± 0.90 cm and a leaf number of 10.68 ± 0.28. Higher fish stocking density resulted in a slower fish growth rate but a faster plant growth rate. It can be concluded that the aquaponics system of NFT with a density of 50 fish/tank could be applied to small-scale livestock. The amount of organic matter that plant roots can use as nutrients is the factor that determines the growth rate of B. chinensis.

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