Hydroponic Flood and Drain Question

I have searched all over the internet and still have not found a good answer to my question about flood and drain hydroponic system water level. I'll give you two scenarios so you can answer my question better. In the first scenario, I have a clone/seedling in rockwool that I transplant into a container that has hydroton as the medium. How high should the water level come to on the rockwool when it fills? I'm confused on whether the rockwool should just touch the bottom of the water level when it floods, or be somewhat immersed. I know that rockwool and hydroton keep water at different rates.

In the second scenario I have a clone/seedling that I plant directly into hydroton using no rockwool, and hydroton as my only media. How high should the water level come to when it fills? Should it come just to the base of the plant? Lastly, would the flood times be similar in these two scenarios or different because of the slight media difference? Thank you.

Answer: S.R.- No matter whether you transplant a rockwool plug into your hydroponic system, or you transplant a clone (or seedling) into straight hydroton grow media, the level of your flood will be the same. During your flood cycle, the water level should fully submerge the root zone. In other words, the water level should come up to, or very nearly up to, the top of your rockwool medium or hydroton medium.

The second issue is the duration of your flood cycle. While rockwool only requires a short soak to absorb the maximum amount of hydroponic nutrient solution, soaking it for a longer period of time will not create any negative effects. On the other hand, expanded clay pellets (i.e. hydroton) require a good twenty minute soak in order to absorb the proper amount of nutrient solution....and if the clay pellets do not get soaked long enough or frequently enough, the medium will not support healthy root growth.

Therefore, the length and frequency of your flood cycle must be made to accommodate the needs of the expanded clay pellets, whether you transplant into straight clay pellets or whether you transplant a rockwool plug into the clay pellets. To read how I transplant clones into a similar hydroponic system, go to this page and scroll down to the "System Setup" section. I hope this helps, and Happy Growing!