Flood & Drain is the hydroponic system that gives you most control over the root environment. The Theory Flood & Drain is so successful because it gives great opportunity to vary the watering (and hence nutrition) cycle. Unlike most other hydroponic systems the roots of your plants are not, in most cases, immediately visible. It is most important to understand what is happening so the correct decision on operating the system is made. With Flood & Drain the growing medium is periodically flooded. During this process any residue of the previous flood will be redissolved in the nutrient solution so that the nutrient solution remaining in the medium after the drain (drain) does not become stale, precipitated or over concentrated (if you try growing a plant in an ordinary pot this is the reason why performance is so often disappointing). Also, because all the free draining moisture is removed from the root area on the drain, vast amounts of air which of course contain essential oxygen is drawn in around the roots. This invigorates the roots and encourages their best performance in terms of growth, water uptake and nutrient uptake.