thats not dwc mate. its nft, "nutrient film technique" i believe it stands for.
in dwc, the roots grow in a bucket full of water and it relies on air stones for oxygen.
in nft, you start them in rockwool cubes for 2 weeks or so then transplant. the roots grow on a shelf above the resevoir with a very slow (3-4 litres per hour) stream of nutrients over them. brought up via pump from the res below. no need for added oxygen : ) i do add some but only a 2w airstone because i realised it stops the roots growing up the tank and blocking the pump. its not neccesary : )