DWC in a nutshell...

The system relies upon an air pump and an air stone to bubble air through the nutrient solution. In the beginning you need to generate spray, so as to get the clay pebble medium wet in order to establish the roots through the net pot.

The water has to be high enough to saturate the clay pebble medium by means of getting it wet or even moist via the actions of the bursting air bubbles.

Once the plant has established a good root system, then lower the level of water in the bucket so that some of the roots can be allowed to hang in the air between the net pot and the water level.

Keep in mind that the bubble bursting "spitting" action of the DWC shoots up several inches. Even when the solution level is 6 inches or more from the lid of my system it's still routinely soaking wet on the under side of the lid.

Just start out with the solution level close to the bottom of the pots. Say about 1". I've had it work well higher than that but it's not any better that way.