Many hydroponic grow systems do not use any media at all (for example Gro-Tanks), the grow systems that do use media are not using the media to supply nutrients, the job of the media is to support the plant physically (hold it upright) and to perhaps hold onto some of the nutrient solution until the next feed.
Hydroponic media are porous, light, and coarse, which allows oxygen and nutrient solution easy access to the plants roots.
Quick guide to growing media:
Clay Pebbles are free draining with high air content. They provide the most oxygen rich environment of all growing media with no risk of nutrient build-up or water-logging.
The popular DWC method uses clay pebbles to support the plants. Growers who want to stick with media should aim to progress to growing in clay pebbles because of the excellent air content.
Coco retains more water than clay pebbles which means there’s less oxygen in the root zone than if using pebbles, but coco does give growers a buffer against not feeding enough, which is why many growers taking their first step to growing in hydroponic grow kits opt for coco, although this is changing now due to the simplicity of DWC and the availability of 60/40 media.
60/40 the best of both clay pebbles and coco.
60/40 provides better access to oxygen than coco and a better buffer against underfeeding than clay pebbles.
Grodan 1cm Growcubes when mixed with clay pebbles provide a well aerated, free draining root environment.
Gro-Tanks and Multi-Ducts are used with Grodan rockwool which provides excellent ratio of air and water.