The current study was designed to evaluate the impact of using digested insect frass (DIF) as an external organic fertilizer on the sustainability of the tilapia-basil decoupled aquaponic system (DAS). The experiment consisted of two treatments; in the first treatment, the digested tilapia sludge (DTS) was used solely as a nutrient source for the hydroponic unit, while in the second treatment supplementation of DIF as an external organic fertilizer (DTS+DIF) was added to the first protocol. The results showed that the concentration of K was higher in the DIF solution compared to the DTS solution. In contrast, Ca was higher in DTS solution in comparison with the DIF solution. No significant differences were detected in all the tilapia's growth parameters between both treatments. Compared to DTS treatments (0.82kg/ m²), DTS+DIF treatment (0.98kg/ m²) recorded the highest biomass of basil. Moreover, the highest chlorophyll content (SPAD) was recorded in DTS+DIF treatment compared to DTS treatment. DTS+DIF treatment produced the highest diameter of the main stem, thickness of fiber strands, phloem and xylem tissues (+16.6, +15.7, +29.3 and +40.65 ±% to DTS, respectively). On the contrary, DTS treatment had a higher vessel diameter than DTS+DIF treatment. To sum it up, it could be concluded that using digested insect frass as an external organic fertilizer may influence the succession of tilapia - basil decoupled aquaponic system.