The tomato is one of the few plants that produces a sufficient quantity and quality of fruit under greenhouse hydroponic conditions to justify the initial capital expense for equipment. According to the University of Arizona Agriculture Department, "The principal advantages of hydroponic-controlled environment agriculture (CEA) include high-density maximum crop yield, crop production where no suitable soil exists, a virtual indifference to ambient temperature and seasonality, more efficient use of water and fertilizers, and minimal use of land area."
Install supplemental lighting from grow lights, along with temperature controls and ventilation. The greenhouse needs to accommodate tomato plants that can grow to 7 feet tall, plus a plant stand that will be 2 to 3 feet high, and grow lights placed at least 2 feet above the plants.
Set up your hydroponic growing system--drip or ebb and flow hydroponic feeding systems work best for tomato plants. Connect the pump located in the nutrient reservoir to the plant tray or drip manifold and attach a timer to the pump. Attach the drain tube from the plant tray down to the reservoir.
Purchase tomato transplants or grow seeds to 6-inch-tall plants before placing them in containers for hydroponic growing.
Shake soil from the seedlings gently and place the tomatoes into their containers. Surround the plants with a growing medium such as rock wool, perlite or vermiculite.
Fill the container to the top with growing medium.
Place the containers on the plant tray, which is seated above the nutrient reservoir.
Set up plant supports for the tomatoes using either netting or trellises.
Add commercial nutrient solution to the reservoir and set the pump timer to fill the plant tray or drip manifold every 30 minutes. Check fluid levels in the reservoir daily and change the fluid once a week. Maintain nutrient pH between 5.8 to 6.3, checking frequently with pH test strips.
Set the grow light timer to provide 16 to 18 hours of light per day.
Vent or air-cool the tomato plants with a fan to reduce humidity and circulate heat evenly. Maintain a light-time temperature of about 85 degrees F. and no cooler at night than 65 degrees F.
Tie growing plants to the support net or trellis using plastic or cord ties.
Hand-pollinate the tomatoes as they flower using a small paintbrush or cotton swab and moving from plant to plant. Do this daily for several days until all flowers have been pollinated.
Cut off side shoots and suckers from the tomatoes with shears to promote vertical growth.
Harvest hydroponic tomatoes when they are either completely red or yellow, depending on the variety.