The quality of the food, especially origin and size, of the only European fiddler crab, Uca tangeri (Eydoux, 1835), was studied over a 2 yr period. In experiments with fluorescent mieroparticles, all particles smaller than 250 μm were ingested regardless of their chemical composition. Comparisons of sediment, feeding pellets and faeces showed that U. tangeri feeds primarily on microalgae which are completely extracted from the sediment. It also consumes vascular macrophytes (Arthrocnemum spp.), macroalgae, detritus and fish carcasses.