Diet (15 g) was put in a nylon mesh bag (100 μm) and allowed it to the bottom of an experimental tank without abalone. The water temperature was adjusted to 19 ± 1 °C. At the end of the allotted time (2, 6 and 12 h, respectively), the remaining diet was removed from the bags and lyophilized for 24 h. Then, the folic acid concentration was measured . The leaching of dietary folic acid was expressed as retention efficiency