it is funny you say that. I do not know about coco but today at the hydro store I met this guy that just started using it and he said he loves it but everytime he checks runoff his tds is 200ppm higher than what he fed it.
I do not know about coco so someone else must answer.
does coco have a bunch of salt in it?
are you supposed to give it a good pre flush?
he said even during the pre flush he would always get a huge jump in tds, no matter how many times he flushed it. Even with all this hell he claims his plants are doing amazing in it. He likes it much better than rockwool which he used to use (I use rockwool).
I would like to learn too. I would like to try coco out.