You can start seeds in polyfill... you know that stuff that is made of pure polyester thread, that they stuff pillows with? I have a faux unit i built that utilizes a spinning disk humidifier's mister.... It doesn't make a true aeroponic environment, because the aeroponic mist thats 50 and below, comes off the impingement pins, with the larger droplets, and its just too difficult to comb it out; however, when the plants start out, they grow completely aeroponically. It's only after the roots get down about two or three inches below the lid of the unit that larger droplets begin hitting them, and the roots convert to water roots as they grow longer. It's a very potent nutrient film technique, due to the enormous oxygenation that goes on from hanging, in between spritzes, and the tiny size of many of the droplets.
I see you're going to use netpots, so for a final medium, the marbles or hydroton will probably be what you use; however just a tuft of the polyfill, about half the size of a bic lighter, is a very, very friendly seed starting mechanism for me; the seeds sense the moisture passing up and past, and come out like gangbusters; the bottom portion of the polyfill will saturate, but its a small amount of water, and it's constantly being re oxygenated by the mist pressing up into, and past. Certainly no root rot problems so far.
I grow mediumless, and go the route of the pool noodle, because i just don't like dealing with medium. The polyfill tuft goes into the center, i spritz with essentially non nutrient water, at first, with the exception that when i p.h. down the water, the last few tenths, i hit it with the old classic General Hydroponics p.h. down, which is a mixture of citric, phosphoric, and nitric acids.. the phosphoric acid gives a little punch for the roots to help them take off. I don't really need to, but that's what i do
the water is always p.h.'d using peat moss. The grow fert is human urine, starting at about 1:50, after the first three or four days, then up to 1:20 or so. Bigbud sprouts in about a day, and in a stacked tub arrangement that gives me a 25 inch rootzone vertically, with a 5 inch crop saver in the bottom, the BigBud roots hit the water in about 24 to 25 days. At 34 days the roots will be about 37 or 38 inches long, already in the shallow water in the bottom. Hybrids tend to not grow as fast as the BigBud of course; that stuff's the real bull of the woods when it comes to taking off like a teenager on steroids. My typical rootgrowth for BB is a little better than an inch a day, for hybrids it's about a half inch a day.
Plants at one month are about 8 to 10 inches of serious bush above the pucks for the BB, about 6 to 8 inches above the pucks for hybrids, same story: Bush City.
When i flip i let them go on human urine and a dash of epsom's salt for a few more weeks. Then, the nutrients become burned banana peels, and burned corncobs; the type of frozen corn you buy at the grocery store are cooked, the corn itself eaten, the cobs are then diced, and burned on the stovetop, to ash.
And away, they go, baby. But... back to the sprouting..
after the seeds sprout, i wait, until they chuck the seedshell. Then, i put the seedling into a rapidrooter plug. When i leave them on just water, they don't take off, nearly as fast; the roots grow, but the sails just don't come out and spread, and take off building a canopy as fast. i notice when i try to put them into the rapidrooters first thing, i often have them die just as they try to chuck the shell.... don't know why, and really it's not a big problem to me to do the polyfill since i have time to switch them out. I only grow eight at a time so it's no biggie.
Sounds like optiquest knows what's up. I'll leave you to your thread, i mainly inserted my starting method for those who grow mediumless, using pool noodle. It's a very sure way to start if you use neoprene pucks or pool noodle, and after all, all you really need is something to support the seed for just the first few days.