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Acute toxicity of antimony pentavalent to neonatal Daphnia magna and the influence of water quality parameters were investigated, and enzymatic activities of organisms at environmentally relevant levels of antimony were determined. EC 50 values of antimony to neonatal D. magna were 90.3 and 63.8 mg/L at 24 and 48 h of exposure, respectively. Dissolved organic matter (FA and HA) and cation (Ca2+, Mg2+ or Na+) had significant protective effects on D. magna against antimony toxicity. With increasing pH in the range from 7.4 to 8.5, increase of EC 50 were observed due to the competition of OH- on biotic ligands. Based on the biotic ligand model (BLM) concept, stability constants for the binding of Sb(OH) 6 - and OH- to the biotic ligand were estimated, and the Log K XSb (OH) 6 - and Log K XOH - were 3.137 and 2.859, respectively. Moreover, antimony exposure in low concentrations significantly increased MDA levels and maybe exert oxidative stress to the organisms. Antimony can also induce toxicity in D. magna by affecting oxidative stress and neurotransmitter systems. The relatively comprehensive toxicological data can contribute to the toxicity prediction and ecological risk assessments of antimony. [Display omitted] • FA and HA weaken Sb toxicity to Daphnia magna. • Ca2+, Mg2+ and Na+ have significant protective effects against Sb toxicity. • Low levels of Sb exhibit oxidative stress and neurotoxicity on Daphnia magna. • Constants for the binding of Sb(OH) 6 - with the competition of OH- was calculated. [ABSTRACT FROM AUTHOR]