One of the more interesting problems that can occur in hydroponic Tomato production is Blossom End Rot (BER). Neither a disease or pest issue, blossom end rot on tomatoes is a Calcium related disorder caused by environmental factors. Blossom end rot on tomatoes comprises two main symptoms tip burn of the youngest leaves, and fruit tissue which looks water soaked and can become black and rotten as the fruit ripens over time. Bottom rot on tomatoes is caused by a deficiency with Calcium uptake from the nutrient solution leading to the plant pulling the Calcium it needs from new tissue (younger leaves an

d new fruit).

The best method of tomato bottom rot prevention is to pay close attention to the following:

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1. Electrical Conductivity (EC) levels:  There is generally a reduction in Calcium uptake under increased EC in the nutrients.
2. Under watering: Plants may look wilted if there is a lack of irrigation due to a plugged up filter, feed pump failure or interruption in the water source which may result in increased EC making it hard for the plant to take up water (and the nutrients from the water).
3. Relative Humidity (RH): A drastic change in RH can change the rate at which the plant is transpiring (the loss of water from the surface of a leaf causing the plant to take up more water and Calcium through the xylem).
4. Overwatering: Overwatering during the winter when light conditions are lower decreases the transpiration rate.  

If this problem has already occurred your best solution is not to take off the affected fruit immediately but to wait a few days while manually adjusting the pH so that while the plants are recovering they do not start to draw Calcium from newer fruit. You can adjust the rate of transpiration by