A technique was developed for the semi-mass culture of the unarmored dinoflagellate, Gymnodinium splendens under laboratory conditions. A maximum cell density of 4600 to 6800 cells ml⁻¹ was observed within 8 to 11 days of culture. An initial feeding test for 8 days with three important marine finfish larvae showed that red spotted grouper, Epinephelus akaara preferred G. splendens fed 200 cells ml⁻¹ with 44% survival. The Japanese stripe knife jaw, Oplegnathus fasciatus, attained 22% survival fed a combination of G. splendens and rotifers (200 cells ml⁻¹ and 5 ind. ml⁻¹, respectively). Red sea bream, Pagrus major larvae did not respond well to the initial feeding of G. splendens alone. Red sea bream were observed to be solely dependent on rotifers (5 ind. ml⁻¹) as initial food. Gymnodinium splendens may be used as a live food in the initial feeding of red spotted grouper larvae (E. akaara) to reduce mortality and to further enhance growth during the critical first few days of rearing.