Abstract: MPA is a new mineral floating agent consisting of 29 alcohol components. The 96-h LC50 for the embryos, fry and fingerlings of the grass carp exposed to MPA were 100-200, 75.86 and 122.77 mg/L respectively. The 96-h EC50 causing teratological symptom of the embryo was 48.98 mg/L. Fry with light kyphosis were able to recover after rearing in MPA-free water. Adverse effects on growth were not observed at the concentration of 6.65 mg/L. MPA of the concentration of 100 mg/L in water reduced by half over a week and was not detectable after 20 days. Effects on the growth of grass carp fingerlings were not observed at the concentration of 100 mg/L during a period of one month.