Nutricuture's Flood and Drain system or Ebb and Flood (as it's also called), is a recycling system that at the set times, solution rises up from the reservoir into the media and pushes out stale air, allowing the roots take up whatever nutrients and water they need. When the flood pump switches off Nutrculture's Express Drain design creates a powerful vacuum which quickly pulls nutrient solution back into the reservoir, with a rush of fresh oxygen-rich air. This fresh oxygen-rich air nourishes the roots leading to more productive growth and bigger yields. The preferred media, clay pebbles, hold very little moisture, so between feeds roots have excellent access to oxygen. Be sure to increase feed timings as the plants grow to ensure they receive enough nutrient solution.
See the video below for a quick overview of Nutriculture's flood and drain(ebb and flood) system -