Purified diets were formulated and fed to four groups of black porgyAcanthopagrus schlegeli fingerlings for 8 weeks. L-ascorbic acid (AA),L-ascorbic acid-2-sulfate (AS) or L-ascorbic acid-2-polyphosphate (APP) weresupplemented to the test diets at 100 mg/kg diet ascorbic acid equivalence. Thecontrol diet was ascorbic acid-free. The result indicated that APP, AS or AA hadantiscorbutic activities. There were no gross signs of vitamin C deficiency inany of the fish fed AA, AS or APP, where as hemorrhagic exophthalmia, ascites,fin hemorrhages, spinal curvature and reduced concentrations of ascorbic acid inblood and liver were found in the control group. Ascorbic acid content washighest in the liver of the porgy fed APP diet. This result indicates that APPhas equimolar activity to L-ascorbic acid as a vitamin C source for black porgy.