Design of aquaponic units
The media bed technique
Media-filled bed units are the most popular design for small-scale aquaponics. This method is strongly recommended for most developing regions. These designs are efficient with space, have a relatively low initial cost and are suitable for beginners because of their simplicity. In media bed units, the medium is used to support the roots of the plants and also the same medium functions as a filter, both mechanical and biological. This double function is the main reason why media bed units are the simplest; the following sections demonstrate how NFT and DWC methods both require isolated and more complicated components for filtration.
· Food and Agriculture Organization of the United NationsSite selection
Site selection is an important aspect that must be considered before installing an aquaponic unit. This section generally refers to aquaponic units built outdoors without a greenhouse. However, there are brief comments about greenhouses and shading net structures for larger units. It is important to remember that some of the system’s components, especially the water and stone media, are heavy and hard to move, so it is worth building the system in its final location.
· Food and Agriculture Organization of the United NationsNutrient film technique (nft)
The NFT is a hydroponic method using horizontal pipes each with a shallow stream of nutrient-rich aquaponic water flowing through it (Figure 4.60). Plants are placed within holes in the top of the pipes, and are able to use this thin film of nutrient-rich water. Both the NFT and DWC are popular methods for commercial operations as both are financially more viable than media bed units when scaled up (Figure 4.
· Food and Agriculture Organization of the United NationsEssential components of an aquaponic unit
All aquaponic systems share several common and essential components. These include: a fish tank, a mechanical filter, a biofilter, and hydroponic containers. All systems use energy to circulate water through pipes and plumbing while aerating the water. As introduced above, there are three main designs of the plant growing areas including: grow beds, grow pipes and grow canals. This section discusses the mandatory components, including the fish tanks, mechanical filter, biofilter, plumbing and pumps.
· Food and Agriculture Organization of the United NationsDeep water culture technique
The DWC method involves suspending plants in polystyrene sheets, with their roots hanging down into the water (Figures 4.68 and 4.69). This method is the most common for large commercial aquaponics growing one specific crop (typically lettuce, salad leaves or basil, Figure 4.70), and is more suitable for mechanization. On a small-scale, this technique is more complicated than media beds, and may not be suitable for some locations, especially where access to materials is limited.
· Food and Agriculture Organization of the United NationsComparing aquaponic techniques
Table 4.2 below provides a quick reference and comparative summary of the various aquaponic culture systems described above. TABLE 4.2 Strengths and weaknesses of main aquaponic techniques System typeStrengthsWeaknessesMedia bed units Source: Food and Agriculture Organization of the United Nations, 2014, Christopher Somerville, Moti Cohen, Edoardo Pantanella, Austin Stankus and Alessandro Lovatelli, Small-scale aquaponic food production, http://www.fao.org/3/a-i4021e.pdf. Reproduced with permission.
· Food and Agriculture Organization of the United Nations