Eleocharis dulcis (Burm.f.) Trin. ex Hensch, is a dominant aquatic macrophyte in acid sulfate swamp ecosystems. This study evaluates morphological traits, population density and ecological dominance using the importance value index (IVI). Field observations were conducted at three stations using line transect and quadrat methods. The species is characterised by upright cylindrical stems (31–183 cm), narrow leaf sheaths, reddish-brown fibrous roots and simple spikelet flowers. The results indicated that E. dulcis exhibited a high relative density (72.79–97.85 %) and relative frequency (27.27–50 %), suggesting an even distribution pattern. Its high IVI values (92.20–148.22) confirm its ecological dominance, whereas other aquatic species such as Salvinia molesta, Hydrilla verticillata and Nymphaea ampla were found in low abundance. The species exhibits strong adaptation to acidic conditions and functions as a reliable bioindicator of low-pH wetlands. It also holds economic value for local communities.