shows the effect of antimony on survival of S. mixtus. The survival of the S. mixtus was adversely affected in Sb-amended media, and the acute toxicity values are also listed in Table 1. The 24-h LC50 value of antimony for S. mixtus was determined to be 4.92 mg L−1. EC50 was not calculated because S. mixtus tends to stay on the surface of vessels without movement, therefore, it is almost impossible to distinguish the immobilization statue between control and exposure treatments. In addition, S. mixtus could not survive when they were tested until 48-h without feeding, therefore the 48 h-LC50 value was not calculated in the present study. S. mixtus seems to be vulnerable to starvation, and exposure duration less than 48 h may be appropriate for the acute toxicity test. As shown in Table 1, S. mixtus (24-h LC50 4.92) is more sensitive to Sb than Moina macrocopa (24-h LC50 12.83). This indicated that S. mixtus could be a better indicator to aqueous Sb pollution.