9

Deep water culture (DWC) is more productive (kg of produce/ m2 growing space) than media-based systems; however, it can be more difficult to manage on a smaller scale. These systems are well researched by the hydroponics and aquaponics industry and are commonly implemented in commercial settings. Leafy greens and herbs, such as basil, do well in this production system. Fruiting crops like tomatoes, cucumbers, and peppers can be successful with appropriate nutrient densities and structural support. The DWC technique may not be suitable for areas where access to supplies or equipment is limited. Rules of thumb for DWC in aquaponics are listed in Table 2.

Nutrient Film Technique: Nutrient Film Technique (NFT) technology comes directly from the hydroponics industry. In this method, plants are inserted into the top of shallow horizontal channels. A small film of water is pumped through the channel, coming into contact with plant roots that utilize those nutrients for growth (Figure 9). NFT systems, like DWC, require sufficient solids filtration to prevent contamination of plant roots. In contrast to DWC, NFT systems need a separate biological filter, as the channel alone does not provide enough surface area for sufficient growth of nitrifying bacteria.

These systems are more complex to design, build, and manage than media-based systems. If channels are not sized correctly, plant roots can disrupt water flow by clogging the pipes. This design assumes a degree of risk, as pump failure can result in large crop loss if water flow does not resume quickly. However, NFT can be a great system for urban areas or rooftops as they are lightweight, use very little water, and can be made from easily sourced materials. Rules of thumb for NFT in aquaponics are listed in Table 3.