A tank field permitting large-scale outdoor testing of diets has been constructed and evaluated. The small size of the tanks in this outdoor microcosm laboratory (OML) optimizes labor and utility costs, thus reducing experiment cost. The OML has been in use for 3 years, demonstrating applicability to a number of research areas, especially feeds testing. Under similar temperature, feed, stocking, and management conditions, shrimp growth, feed conversion ratio (FCR), and survival values closely reproduce those measured in production-scale round ponds.