Interesting article ...thanks JCO

they could not use the nutrient-rich fish water to grow the basil, because there was no safe, economical
way to purify the runoff which comes into direct contact with the edible leaves.
-I added the underlines to key words-

The way I read it...The Basil 'would grow' in the water from the FT's. It was the.. well, the 'fish poo water' getting on the leaves (the edible part). 'That' was the problem.

Where the 'runoff' was/is comming from(?) ...I don't know.

I do remember in one of the videos of a commercial operation, they were (overhead)spraying/misting the new lettuce seeds, in the rafts. They did this because the seeds were not getting wet, from the water below. I belive they did it till the plants were large enough, till the roots started to come out the bottom of the rafts.
EDIT:
Wow,I found the video I mentioned....it is a hydroponic video. 'See' just before the 2 minute mark. I don't know if they are spraying 'fresh water' or not ? Just thought, 'maybe' this was where the runoff in JCO's article was comming from (?)
Hmmmmm.....the fish tanks could be just outside of where they are growing all that lettuce...