Mosquitofish are widely used for biological control of mosquito larvae in rice fields, but the presence of different types of vegetation or alternative arthropod prey affects the performance of the fish. Feeding experiments were conducted in 4 rice field vegetation zones. Overall, predation was maximal in young and mature rice, moderate in the submerged naiad vegetation, and minimal in areas of open water. A preference for fourth instar Culex tarsalis mosquito larvae over Daphnia pulex and the amphipod Hyalella azteca was demonstrated. Second nymphal stage corixid bugs, Cenocorixa sp., were avoided; a similar notonectid, Buenoa sp., was eaten in amounts comparable to the D. pulex and H. azteca. No preference between Culex tarsalis and Anopheles freeborni mosquito larvae was detected.