Free because it's long to print.
Plug in a good aquarium air pump 3 Watt MINI, put in clay balls, fertilised liquid (in all garden shop)
and you can growing big plants with a small system (Spiral Twist : big surface roots in small space).
It's automatique, no need suveillance.exept for the liquid 1.3l, you must change it every week..
Make it in dark abs (for the light), pla is eated by water in the time.
You can put an economic lamp for winter and programator (no need to drain all the time...)