AQUATOX is an aquatic ecosystem simulation model developed by Environmental Protection Agency (EPA). Its main goal is to predict the fate of nutrients, organic chemicals, and sediments in different water bodies (e.g. rivers, lakes, estuaries), as well as their effects on the organism characterizing the ecosystem (fish, invertebrates, and aquatic plants).  AQUATOX can simulate fundamental processes regarding the partition of chemicals in the different environmental compartments and within the trophic chain, and their direct and indirect effects on ecosystems in terms of variation of biomass through the time.

More information and the executables of the model can be found at the official AQUATOX website:

http://www2.epa.gov/exposure-assessment-models/aquatox