I had wondered whether we'd see a decrease in plant health and robustness along the flow of the bed as the water lost oxygen along its route. I think we're seeing a slight hint of that effect: the corn towards the beginning is bigger and yellower, while the corn towards the end is smaller and greener. I think what's happening is this: due to decreasing oxygen levels, the corn towards the beginning is growing faster than the corn toward the end; and since the grow bed is new and lacking in sufficient nutrient buildup, the faster-growing corn is yellower since, due to nutrient deficiencies, its rate of growth is outstripping the rate at which it can manufacture chlorophyll.
It's interesting to note that the system is so nutrient starved (due to having so few fish in it so far) that the aquaponics corn is lagging behind the outdoor sample of the same variety that was planted at the same time:
The corn I grew in my small aquaponics system last year grew about 50% faster than the corn I grew alongside it in the dirt garden, and I have little doubt that the current larger system will produce similar results once it gets better established.
