Thanks for all the links and pointers! And yeah, now that I know the term "NFT hydroponics" that is exactly what I was imagining, just didn't know what it was

Thanks for all the links and pointers! And yeah, now that I know the term "NFT hydroponics" that is exactly what I was imagining, just didn't know what it was called. "i want plants that are plugged into the matrix. living in a fake reality, the organic component of a larger machine that nourishes me.". As for NPK, I (obviously) don't know what I'm talking about, but I'd really want to do something optical. For one, I think you're right, it strikes me as bad to use electrical conductivity to measure both hydration, and relative concentrations of ions, and two, optical just seems ... cooler... to me. In theory, you can "just" use 3 tuned LEDs and a photodiode... Wow, that last link is... now my standard to strive towards for project writeups.