| In many hydroponic applications the medium is mostly a method of supporting the plant's weight. It often functions as a way of retaining nutrient solution, but in some applications this is considered a "bonus". As long as there's a way to support the crown of the plant, keeping it stable, there isn't any need for a medium. In my DWC system the medium is there just to support the plant. The roots grow down into the solution and that's where they get all the food and water they need. Anything stored in the medium isn't important once the plants are big enough. In NFT systems in particular, and often in other applications, the plants are supported by neoprene collars. These are basically little neoprene disks with a cut from the side to the center so that it can fit around the crown of the plant like a skirt. This collar is slightly larger than the hole the plant is lowered into, so it holds the plant in place. Also, pretty much every hydroponic system is going to have problems with power outages. Aeroponic systems and NFT are especially vulnerable. Ebb and Flow can go a long time, particularly if the power goes out right after a flood cycle. DWC can probably go the longest without power, but it still won't go forever. Only Autopots and wick hydroponics can really run without power for long (both require no electricity at all). | 
