The ecological Tidal Model EcoTiM is a complex ecosystem model which dynamically simulates the cycling of organic carbon, nitrogen, phosphate silicate and oxygen within the back barrier system of the East Frisian island Spiekeroog. The model has the capability to resolve the seasonal cycles as well as tidal processes. It consists of several interlinked modules describing the pelagic and benthic foodweb, the microbial loop including the distribution of detritus. The description of the biochemical and ecological processes bases mainly on ERSEM.