This study aims to qualitatively analyze the bioactive compounds in Eucheuma cottonii seaweed flour extract and its application in commercial feed for tilapia (Oreochromis niloticus). The methodology employed is experimental and consists of two phases. Phase 1 involves the extraction of E. cottonii flour using three different organic solvents with varying polarity (ethanol, ethyl acetate, and a combination of ethanol + ethyl acetate). The testing parameters include qualitative phytochemical tests for alkaloids, steroids/triterpenoids, saponins, flavonoids, and tannins. Phase 2 consists of the application of the extract to tilapia over a 30-day rearing period with four treatments: control/commercial feed (P0), commercial feed + ethanol extract (P1), commercial feed + ethyl acetate extract (P2), and commercial feed + combined ethanol and ethyl acetate extract (P3). The parameters tested include absolute weight, specific growth rate, survival rate, and water quality. Phytochemical and water quality data are presented in table format. Meanwhile, growth and survival data are analyzed using ANOVA, followed by Duncan’s test for significant differences. The results of the researches carried out, it can be concluded that the phytochemical analysis of E. cottonii extract in ethanol and the ethanol + ethyl acetate combination yielded similar compounds: alkaloids, steroids/triterpenoids, and flavonoids. The ethyl acetate extract contained triterpenoids and flavonoids. Both saponins and tannins returned negative results across all organic solvent treatments. All treatments with the addition of E. cottonii seaweed extract in various organic solvents demonstrated better growth in tilapia compared to the control treatment.