Hydroponics is a form of gardening in which plants are grown without soil, either with their roots suspended free-floating in a liquid nutrient solution, or supported by a soilless substrate in a chamber flooded by liquid nutrients. Hydroponics is used to grow vegetables in inhospitable climates, such as scientific research stations at the Arctic Circle. For commercial production, hydroponics is used to grow tomatoes. Because the plants get all the nutrients that they need at the optimal time, hydroponic tomatoes grow larger and produce more fruit than plants grown in soil containers.
Place tomato seeds ¼ inch deep in a rockwool substrate cube to germinate. Place cubes in a bowl of warm water and place bowl on a plant heating mat to keep the water at a constant warm temperature. Tomatoes germinate best with water that is at 64 degree F.
Keep plants under grow lights that are rich in red and blue spectrum light. Lights should be turned on between 14 and 18 hours daily.
Transplant seedlings into larger rockwool flats approximately 14 days after sprouting by making a hole in the larger rockwool cube and placing the entire smaller rockwool cube inside of it. Water plants by flooding the seedling growing chamber with water-and-nutrient solution.
Continue to transplant tomato plants into larger cubes any time that tomatoes grow too large for their current cubes. If plants become too leggy, turn the cube over so the tomato bends upward in a U shape. Plant the cube upside down in this manner. The buried tomato stem will sprout roots and continue to grow.
Transplant tomatoes into a final growing media such as vermiculite in the hydroponic growing chamber before they flower.
Check the nutrient solution in the growing chamber with the probe of a pH testing meter daily. Adjust pH of the solution as needed by adding phosphoric acid to lower the pH or potassium hydroxide to raise the pH. Never attempt to change the pH more than 1 degree at a time. Doing so can damage the plants.
Use an EC meter to check the strength of your nutrient solution. Too many nutrients can burn a plant, but too few can starve it. Add nutrients or water as needed to strengthen or dilute your nutrient solution.
Change the solution in the hydroponic reservoir every two to four days.