A light fixture for use as a horticultural and agricultural grow light fixture, which includes a fixture housing, end panels disposed in the open ends of the housing, each of which includes a duct opening and a duct connector disposed in the duct opening. A specular insert is installed in the interior of the fixture housing and includes sides spaced apart from the sides of the fixture housing such that a cooling and insulating airspace is defined between the specular insert and the housing. Both the housing and specular insert are mounted on a base, and the fixture bottom opening is covered by a lens. In the preferred embodiment, an adjustable light socket assembly is positioned in one of the duct connectors. Finally, the assembly includes a adjustable vent hole cover mounted in each of the duct connectors. The vent hole covers can be adjusted between a fully open position and a fully closed position, such that when the duct connectors are connected to an air circulation system, the rate and volume of air flow to and within the interior of the light fixture can finely adjusted.