Four fish tanks were part of the same system and should be considered one experimental unit. It is typical for aquaculture systems to have more than one tank so that fish at varying stages of development can be raised and harvested in a staggered fashion. The mechanical systems and their energy demands are reported in. Mechanical components drawing electricity were a water pump, an air blower, four in-tank electrical water heaters, a 4-ft wall-mounted greenhouse fan, an inflation blower to maintain a pillow of insulation between the layers of greenhouse film, several box fans to distribute air throughout the greenhouse, and fluorescent lights. In cold weather, thermostat-controlled, propane-fired space heaters maintained the air temperature at no less than 4–7 °C. If the water temperature dropped below 22 °C, the thermostat-controlled electric heaters operated.