There is also a water pump that feeds each net until the roots are well establish in the water.
Check out the bill of material.
True DWC doesn't have that that makes it bubbleponics The splattering of water droplets and A Spray bottle for the Top will do just fine
All At Walmart
Rubbermaid 4$
Air pump 7$
Air-hose 3$
Air-Stones 3-6$
Reflective Survival Blanket (Mylar) 3$
CFL's 2-15$
Lamp Kits(cord,Socket) 6$
Light socket Y Adapters 2$
Room Thermometer/Hygrometer 6$
Fish Tank Thermometer 3$
Fish Rocks(Grow Medium) 4$
Hydro Store & Online
150w HPS 80$ Online
Netty Pots .25$ Hydro Store
Nutrients 30$ Hydro Store
PH Up & Down 20$ Hydro Store
Ph Tester (Liquid) 6$ Hydro Store
TDS Tester(Stolen) Otherwise 25-200$
Thats pretty complete list of my stuff there and current Prices ....Hope It helps