NFT channels are designed for growing small leaf crops such as lettuce and small herbs, but growing larger plants such as tomatoes, cucumbers, beans, and peppers in NFT channels is difficult, if not impossible. Large plants are usually more of a “long term” plant and need more root area than an NFT channels offers (they can also capsize the channels), so hydroponics (a lot of very large growers use hanging gutters and rockwool slabs. However for a smaller grower without all of the monitors and alarms, those rockwool slabs could dry out if the injection system failed in any way or was just not feeding enough to a growing plant. It is very difficult to “re-wet” it completely. Even if you flood it with water the water will tend to just wet area right around the roots. The water is looking for the easiest path and just flow along and around the roots. That is bad because as the plants continue to grow the roots will not branch out into the dry areas.