I know this subject is not pertient to HP aero, but, I think it appropriate for everyone currently on this thread.
Reading on a DWC journal, I noted the PH crept up about 1 everyday with a 6 gal. resevoir and mature plants using 1 gal. of liquid a day.
I thought of 2 reasons. First that the plants were using minerals causing the increase, which didn't make much sense. Then, I postulated that it WASN'T a closed system. They were introducing outside air containing CO2 into the air stone and nute res. The CO2 is retained by to nute solution as carbonic acid in ever increasing amount. So... wouldn't it be better to close the system and use, mostly, the res air space for the air pump supply? I assume it would correct injecting more and more CO2 into the nute supply.
This may show why DWCers replace the nute solution weekly or so. It's not lack of nutes but accumalation of carbonic acid. Any thoughts?
On the ultrasonic transducer atomization front: I haven't had much success with Chinese suppliers. A Korean firm has the right transducers and I'm pondering rolling my own fixture, controller, power supply (yeah, the whole shebang). It's not rocket science. AND, I've learned from this journal that redundancy and power backup are critical features. Thanks.
Lastly, Sherri, yes some studies (unfortunately, I can't cite them) show ~23% more THC production with UVB lighting. Apparently, some cannibols are converted to THC. The paper is in the list I posted previously. In the '70s THC of 4% was intense. Today some strains are producing 20+%.