When setting up a growing container, you just not simply stop at pouring some growing media. The entire process is a lot more complicated and it has a delicate nature. The entire process is based on a flood and drain technique, which constantly fills the bed with water and drains it.
The first part of a media bed is represented by a dry zone. It is 2 to 5 cm thick and is designed to act as a barrier between the light source and the water. If the water manages to be in direct light, there are increased chances for the system to develop algae. These green microscopic plants can transform your water into a maze of green that has a dull smell. Another role of this dry zone is that of protection against harmful bacteria. Those can seriously damage the root system and prevent proper development.
An intermediate zone is the one represented by a combination of a dry layer and a wet one. It is about 10 to 20 cm wide depending on your entire system. This area is responsible for the proper flooding and draining of the roots. Here is where you will have the majority of activity going on. This zone is crucial for the proper growth of roots and for the gas exchanged. Some recommend placing in this area some worms which will be responsible for devouring the rest of the nutrients a plant can`t absorb. Furthermore, they will act as a cleaning agent that will make sure there are no dead roots in the area. So, if you want your system to be smooth, worms can help you avoid clogging.
The last part is the wet area. This is the bottom of your growing bed and it has around 3 to 5 cm. As you may guess, this is always wet and it is destined for the accumulation of solid wastes. Here is where the process of mineralization happens. Also, various benefic bacteria find their home here because the wet environment helps their development. It might seem not so important, but it is. The wet zone helps in decomposing any solid waste which will prevent your system`s failure.
Bottom line, when setting up a growing container, it is not enough to place some growing media. You need to consider the different stages the water goes through along with how the roots will react. If there are not specific areas for the process to go through its normal course, you will experience difficulties in harvesting healthy plants.