Quote Originally Posted by SpaceNeedle
If paperchaser gets his DWC going, and he has a plant sitting in a net pot with a 5" rockwell cube sitting in some clay pellets, and if there are none or very few roots coming out of that 5" cube, he runs the water level in the bucket right up to the bottom of that rockwell cube, there is no way that plant is going to thrive.
There's this little thing called capillary action - aka wicking - that comes into play, especially with rockwool. If the bottom of the cube is touching the water it will wick the water upwards to the plants roots.