Soon as the plants start rooting heavy you dont get much floating. The root hair atach on to the hydraton as it goes from wet to dry. The whole tray becomes one breathing feeding system once set in and dont take long to do. To be honest it was awhile back but I think the trays used to be filled to the top and the flood would just hit t that level or just below. Drain back out the same way in, no overflow just on precise timers. Worked well
It works but it is a total shit show after harvest. Ive tried it before and the results with the plastic top are better in my experience, root zone stays dark and humid and grows a thick mat of roots.
Had police turn over my trays once. Only three weeks in veg. There was a huge block of roots over a foot thick and a 150cm x 100cm. Your right about after harvest wen cleaning them, beter to just use new. We ended up using the iws pro flood and drain system in the end. But again it is still a headache cleaning out roots from any amount of hydroton, even 10ltrs of them. Ended up blocking a few bath tubs drains.
I've been doing this. Last time I used rockwool slabs and this time I'm using a bunch of 6" coco cubes pushed together into one big square. I wasn't planning on doing this time, but I was getting algae. I just got done about an hour ago actually.