What types of hydroponic systems do hydroponic vegetable farmers use?

Answer 1

http://www.hydroponicsonline.com/lessons/table-of-contents.htm

http://www.cropking.com/cgi-bin/cropking/start/apps/store/start.html?gclid=CK2_jo_cwocCFQZYHgodj3n6IQ

http://www.hydroponics.com/hydroponics/index.html

Answer 2

a timer, pump, and electronic valves...

you fill the tanks with nutrients... let stand for a predetermined amount of time... drain and let stand until the next fill...

I saw one that was made in an aquarium.. even used aquarium gravel that was brightly colored!! Plants were rooted on paper towels and transplanted into the nutrient bath tank.. everything was solar powered with a boat pump used to fill the tank and some clothes washer electrically controlled valves used for filling and draining the tanks.