Hydroponic tomatoes are grown in greenhouses, where the climate and culture are controlled and there is no natural wind movement to assist in the pollination process. Tomatoes, unlike many plants, do not depend on bees or other insects for pollination, although bumblebees are used in some greenhouses for pollination. Tomato plants simply need movement or "vibration" to spread pollen from one flower to another, because the male and female flowers are found on each tomato plant. The method of vibrating tomato plants depends on the size of the hydroponic growing operation. For a small operation, the technique is simple.
Wait until tomatoes are flowering and some flowers are fully open. This means the female flowers are receptive to pollination.
Walk down a row of tomato plants, tapping them gently with a smooth stick until you see the fine pollen dislodge from the male flowers. For more complete pollination, gently thump the area just above the flower cluster to help release more pollen.
Repeat step 2 every other day during the growing season.