Could that by why your roots aren't still white as can be at harvest time? IIRC, the vast majority of the oxygenation of a liquid occurs at the surface; IOW, it doesn't matter if a tank is two feet deep or ten, since there isn't much benefit from the bubbles traveling up through the liquid. Err...
I think? It's the turbulence at the surface, the multiple bubbles "breaking." I have gotten the impression that the same amount of DO ("air"), delivered by way of more - but
smaller - bubbles gives the most value, due to the ability to provide a more turbulent surface interface.
That could all just be a steaming pile of horsesh!t, though
.
I dump the growing bucket's remaining contents down the commode.
Probably the only thing I have against DWC. At reservoir change time, it becomes just another drain-to-waste hydroponic method. I used to try to pour mine outside (as and when I could) so that the plants in the garden could have a chance of wringing the last bit of nutrient out. But I must confess that I've dumped my share of nutrients into the sewer, too, in the past. Visiting the local wastewater "treatment" plant and realizing just how much stuff goes right through it, untouched, and then directly into our natural water systems... was a real eye-opener. It was almost like they weren't doing anything (FFS!) - just letting micro-organisms (and some that could be seen with the naked eye) eat what they could of the organics, then running all the solids (undigested feces remnants, about ten billion cigarette butts, coins, jewelery, the (very) occasional finger/fetus, et cetera) through the giant press to remove all (that they could) of the last bit of liquid from it, then into the big dumpster for haul-out. Everything else... to the river! Because, hey, it's not like we - and all the other communities downstream - get our drinking water from the river or anything <HEROIC EYE ROLL> .