Changes in food composition of 12 species of fishes from the southeastern part of the Ciénaga Grande de Santa Marta, Colombia were evaluated; a total of 2035 individuals were sampled. Significant changes in food composition with size, time and space were observed, mainly in Ariopsis sp., Cathorops mapale, Lycengraulis batesii, Astyanax magdalenae, and Aequidens pulcher. Regarding diet similarity between species, two main groups were observed. The first one was divided in three subgroups: one characterized by fish foraging on insects and zooplankton is composed by A. magdalenae and Roeboides dayi; the second one is composed by the generalists Ariopsis sp., L. batesii, and A. pulcher, and the third one by fish predators Caquetaia kraussii and C. mapale. The other group was characterized by fish feeding on phytoplankton and in a lower proportion on detritus and zooplankton (Oreochromis niloticus, Mugil incilis, M. liza, and M. curema) or on detritus (Cyphocharax magdalenae).