I built a DWC hydroponic system in order to grow some sweet basil! I used a plastic bin that I purchased specifically for this project. The only problem that I had with it was that the plastic sides were translucent and the top was black. I spray-painted the sides of the bin black to make it opaque, and then I spray-painted the sides and top of the bin white so that it would reflect light. It needed to be white so that the water inside the bin stays cool under the bright light.
I then drilled 15 holes on each side of the lid for the net pots to sit in. The number of sites was determined by the size of the container that I was using, so if you do something similar, you might have a different configuration. My goal was to have a DWC system that I could also use as a cloner, but unfortunately my neoprene discs are slightly smaller than the holes I need for the net pots. I'll have to save them for a later project.
Out of the 30 available sites, only 28 ended up being used for mature plants. The site at the rear-right is being used for the air lines which are connected to the airstones at the bottom of the bin. Another site in the front row near the center is being used as access for filling and testing.
The first image shows the bin being used for germination. I hadn't hooked up the air pumps yet, and the bin is far from the light.
The second image shows the unit in operation. The air pumps are suspended from the same closet bar on which the light is hanging. When I first started the system, I put the soil-grown basil on top so that I wasn't wasting as much light. I also put down a rectangle of mylar on the seam between the lid flaps in order to retard algae growth, which requires light. On top of that I constructed a cardboard prism covered in mylar to reflect light 90' outwards instead of having it bounce back up towards the light. I can tell that it was effective because all of the plants in the inner rows leaned towards it as they grew taller.
As you can see, I'm using a neoprene disc in the one net pot to block light at the unused growing site. That's my access for adding nutrients, and to be able to see the roots. At this point, all of the plant's roots have grown in to a monstrous mess. I'll add a picture of them once I do the last harvest.
The last image is the system as it currently stands. I just changed the water last night, so the system is full. I turned the HPS off for the pic, because as you can see by the previous image, the colour balance goes out of whack on my camera.
This is how it looks a few days before I harvest. I don't let them get too tall, and this picture was taken about a week after the previous harvest.
While I haven't weighed anything, this seems to be a good amount for a family of basil lovers to enjoy pesto a few times a week. If you're considering growing hydroponic basil, I suggest a DWC system, but with slightly larger spacing, as my plants are a bit too close together.
For this cycle of growth, I maintain a water level that is about an inch below the net pots. I check the nutrient strength and pH daily, and try to keep the nutrients somewhere between 700ppm and 1000ppm, with a pH somewhere between 5.5 and 7.0. If you go too far outside of those ranges, the plant will start to suffer, and the nutrients can come out of solution as a precipitate. While you can do this kind of gardening without testing equipment, having a TDS meter and pH meter makes it a lot easier to make adjustments, as the nutrient strength doesn't change linearly with the water level. I use a 2 part hydroponics nutrient solution, as well as humic and fulvic acid additives. I'm using tap water instead of RO, so I haven't been adding very much Cal-Mag. Your mileage may vary!
UPDATE: I've harvested that lot, so as promised, here is a picture of the root system after the water was drained (I used it to feed soil plants where possible). I got some help from my niece, who you can't quite see. Be patient, as it's an animated gif so it could take a while to download.
Let me know in the comments below if you have any questions or comments!