Lighting is key to successful hydroponic growing. I recommend HPS (High Pressure Sodium), MH (Metal Halide), or fluorescent lights. HPS emits more of an orange-red spectrum of light, perfect for flowering and budding. MH are high in white-blue-green spectrum, they're good for the vegetative (grow) phase, or plants that never flower. HPS lights are one of the most effecient lights made. They provide the highest lumen to watt ratio and last for years with minimal degrade in performance. MH are also very good. I heard they lose about 10% effeciency in the first year of regular use. You can buy conversion bulbs to operate on either ballast. Some bulbs are hybrid and incorporate both spectrums. I recommend the 430 watt son agro for small-medium gardens, 600 watt for medium gardens, and 1000 watt for large gardens. HID (High Intensity Discharge) lamps like MH-HPS produce about 4-5 square foot growing area from 400watts of power, 600watts=7-8 ft., 1000 watts=10+ft. Depending on reflector used. HID's generate excessive amounts of heat, which can be good in cold temperatures. If not, cooling systems must be used to keep your air temp around the plant approx. 20 degrees C or 72F during the day and 17C or 66F at night. The light should not be too high so the plants stretch for it, and not too low so the plants wither or burn. Most fast growing plants can be acclimated from 3 feet to a distance of a foot for a 400watt lamp. Do this over a period of time. Keep a fan oscillating lightly hitting plants day and night to help there root system grow strong. YOU MUST HAVE A FRESH AIR SOURCE. Air circulating in from outside and then sucked out via blower, fans. etc. or open a window. If you dont provide this necessity, you might as well grow without ventilation in soil. EXCEPTION, when using CO2 (Carbon Dioxide) turn off ventilation timers or close windws. Also don't allow roots to be exposed to CO2 cover with lid or plastic wrap. If you use an air pump move it to fresh air location. I only use fluorescent lighting for seedlings, it doesn't generate much heat and is economical. The sun is also very economical, yet it is not, as consistant. When using hydro outdoors make sure resevoir is not in direct sunlight. Your nutrient temp should be around 22 degrees C and 76 F. If not you'll notice your plants suffering.