The tomato plants in the ebb and flow table have been growing really well in the last couple weeks. However yesterday I noticed that some of the leaves have turned purple and the main stem was discolored and shriveled towards the base. After some research I determined that the likely cause was a phosphorus deficiency. Phosphorus deficiency is common in soil grown tomatoes and sometimes is caused by the soil being too cold. The temperature of the water in the system was at 62 Degrees Fahrenheit, so I used a small aquarium heater to raise the water temperature to 73 Degrees F.
Over the next week I will continue to observe the tomatoes, with the only changed variable being the temperature of the water. My plan is to determine whether using only the water from our aquaponic systems and heating it to 73 degrees will the deficiency be reversed or must we supplement the water with a phosphorus additive. There are hydroponic solutions on the market containing phosphorus and other nutrients and I am currently looking into natural sources of the electrolyte. Does anyone have any ideas?