It took a few days to get motivated enough to plant, but it's done. I planted five lettuce seeds and five spinach seeds (from no-name grocery store seed packets), each in their own 1" rockwool plug. The seeds are about half an inch above water level, though the rockwool does an excellent job of wicking moisture up. I am using the lettuce nutrient pack from five-gallon-bucket hydro.
The spinach has not sprouted yet, but I had lettuce sprouts by day 3 (fully a week before the package indicated). Pics after the jump.
Day three, full tray:
Day four, full tray:
Day three, close-up of one seedling showing extensive root fibers:
The location offers a few hours of natural sunlight. Temperature has varied from about 70 °F to about 85 °F, so a bit warmer and less stable than the ideal. The tray is a disposable aluminum steam table pan, full table sized. I filled it to about 1/2" from the rim with pre-soaked clay pellets, added solution until they started trying to float and then stuffed the seeded rockwool plugs into finger-holes. I mounded up extra pellets around the sides to stabilize the plugs.
Nutrient solution was 1200 ppm at addition (way higher than ideal, but was according to directions in the nutrient pack) and has not changed since then. The water level has not changed (as expected; the whole setup is enclosed in a zippered plastic 'tent', so water vapor escape should be minimal). As soon as I saw green I added a full 5-meter strip of red LED lights to the 1-meter 'bright white' strip, bringing the supplemental lighting to about 75 W on a 14-hour timer. This is probably not ideal for the spinach which has not yet sprouted.
As you can see from the close-up some of the sprouts still have their seed coat attached, which means I did not shove the seed far enough into the rockwool. The full tray pictures are rather boring at this stage, with only a few leaves peeking over the edge. Even so, my youngest daughter is excited to see her plants grow (she seeded the plugs, so obviously they are her plants now).