Abstract: The invention provides an improved modular aquaponics system for growing plants and fish together in a closed system whereby fish tank waste water is utilized by the plants as a source of fertilizer, thereby clarifying the water before returning it to the fish tank. The improvements comprise an improved plant grow tray, a prefabricated, “snap-together” grow tray system, an energy-efficient calibrated air displacement pump and a fish waste water clarifier having a baffle.