Among cultivators of the media bed aquaponics, the agreed depth of the grow bed is 12 inches. This measurement is reached as growers factor in the various zones that comprise the plants' grow bed. However, shallow and deeper beds may also be utilized depending on the plant variety you aim to cultivate.
What is a media bed aquaponics?
Media bed aquaponics is an aquaponics method that utilizes fish, grow beds, grow media and plants. These components work together to provide a closed-loop system with continuous nutrient flow and waste filtration in a repetitive process. The grow bed refers to a container that stores the growing medium, which might be volcanic gravel or clay pebbles.
In the media bed method, the grow medium functions as an anchor and support to the plant's roots while simultaneously acting as a natural biological filter for all water passing through the system. The fish are kept in separate tanks, and their waste is poured into the grow beds, where it provides essential nutrients to the plants.
How does media bed aquaponics work?
The media-based system comprises a grow bed filled with growing media (such as expanded clay pebbles, gravel, and lava rock) and into which the vegetables are sown. Water from the fish tank can either be pumped or gravity-fed into the grow beds, allowing the plants to consume the nutrients. The porous nature of the grow media will enable them to hold water for extended periods, allowing for more efficient nutrient uptake while also filtering the water to keep sediments and other creatures out of the fish tank.
The grow bed serves as a mechanical and biological filter and region of mineralization. The nitrifying bacteria colony is likewise housed in the grow beds, serving as a growing space for the plants.
The water travels to the sump tank by gravity as it exits the grow beds. The water is now clean and solid-free, and it is pushed back into the fish tank. The water entering the fish tank raises the water level, causing it to overflow into the grow beds and complete the cycle.
What is the relationship between media bed and fish tank in aquaponics?
The size of your grow bed is directly proportional to the size of your system. This fact is because the amount of fish waste determines the number of plants you can grow. Moreover, the quantity of fish you culture affects how well the plants thrive. Fish produce ammonia, converted to nitrites and subsequently nitrates by bacteria on your growing media, which the plants need for sustenance.
An oversupply of ammonia and nitrates will result from too many fish or too much fish food; if you don't have enough grow bed medium, the water will slowly harm the fish. You will not have enough nutrients for your plants if your number of fish is not enough.
What are the zones of an aquaponics media bed?
There are three grow bed zones in a media-based aquaponics system, each with its own set of functions.
- Zone 1: This is also known as the dry zone and is located within the first 1 - 2" (5cm) of the grow bed and serves as a light barrier, preventing direct sunlight from reaching the water, leading to algae growth. It also inhibits the growth of fungus and other harmful bacteria at the base of the plant stem, as beneficial bacteria are sensitive to direct sunlight. Lastly, this region helps minimize evaporation from the beds by shielding the wet zone from direct sunlight.
- Zone 2: Growers call this zone the root zone since this is where the plant roots grow and where all other activity occurs. Zone 2 is the portion of the grow bed that is flooded and drained regularly, and it is located around the 4 - 6" (10-15cm) mark. When it's time for the flood and drain cycle, the incoming water helps disseminate moisture, nutrients, and incoming solid fish waste particles into the region. In contrast, the drain sections let the water drain entirely, allowing for efficient transport of oxygen-rich air into the plant's root area. This zone is where the worms break down and minimize solid waste, releasing nutrients throughout the system.
- Zone 3: The last zone, which is in the bottom 2" (5cm) of the grow bed that is permanently wet, is where the small solid wastes accumulate, so the organisms most active in mineralization are found here, breaking down the waste into smaller fractions and molecules that the plants can absorb through the mineralization process.
What is the recommended depth of media bed?
Experts recommend a conventional media bed depth of 12 inches for the several zones that make up the little artificial ecosystem. Most experts feel that this level of detail should be sufficient to keep your media bed aquaponics running.
The root systems of the plants will be well-supported at this depth. Anything beyond that is frequently useless and wasteful of resources. Not to mention that as the bed grows heavier and thirstier for water, it will become more challenging to maintain.
On the other hand, a deep grow bed is more expensive than a shallow grow bed since you must fill in more of your preferred media. You'll also need to consider the additional cost of supporting the weight of a deep grow medium bed, as well as the overall volume of water required in the system to irrigate at that depth.
But do remember that shallow beds are ideal for growing short-lived plants, such as lettuces and greens. They do not work well with firmly rooted plants like cucumbers, indeterminate tomatoes, melon, and corn. These plants need appropriate nutrients and microbes. Shallow beds lack the necessary foundation and area for broad root zones.
Suppose you decide to go for a deeper grow bed; remember that this could be more expensive given the fact that you will use more growing media.
The depth of an aquaponics bed has its limits, be it shallow or deep. What bed depth is most appropriate for you depends entirely on your demands and situations. Shallow beds are suitable for cultivating short-lived plants. However, if you want to grow plants with deep roots, you'll need additional depth in your beds. As already stated, the 12-9nch rule applies here.