In a media bed, there are three aquaponics grow bed zones, and each zone has a different purpose and responsibilities.
The generally accepted standard for the depth of a grow bed is 30cm deep (although some aquaponics gardeners will use shallower or deeper grow beds).
This allows for a more robust system since the bed rarely has to been cleaned out because the depth allows for a more effective breakdown of solid waste.
It’s a good idea to learn what each zone does as it’ll help you to understand a bit more about the aquaponics cycle.
Zone 1 – The Surface Or Dry Zone
The light penetration and dry zone area is within the first 5cm of the grow bed. This dry area minimizes evaporation and prevents collar rot in the plant base.
By ensuring this area remains dry, the formation of algae is also prevented from forming on the surface of the media while moisture related plant diseases such as powdery mildew are minimized.
Zone 2 – The Root Zone
In the next zone of around the 10-15cm area, root growth and plant activity will be the most prevalent. When it’s time for the flood and drain cycle, the drain part will allow the water to completely drain away.
This allows for efficient delivery of oxygen-rich air to everything in that zone which includes the plant roots, soil microbes, good bacteria and composting worms.
For the flood part of the flood and drain cycle, the incoming water helps to spread moisture, nutrients and incoming solid fish waste particles throughout this area.
The worms in this area are responsible for breaking down and minimizing solids which in turn releases nutrients and minerals through the system.
Zone 3 – The Solid Collection & Mineralization Zone
In the last zone, which is the last 5cm of the grow bed, collects fish waste solids and worm castings. You need to take into consideration the width of your grow bed as you’ll be tending your grow bed from either one or both sides.
The main importance is having access to all areas of the grow bed. Most people are comfortable reaching across to about 0.75metres. If you can tend to both sides of the grow bed then you can use a much wider bed with access still being easy.
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