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Typical coupled aquaponic system range from small to medium scale and larger sized systems (Palm et al. 2018). Upscaling remains one of the future challenges because it requires careful testing of the possible fish and plant combinations. Optimal unit sizes can be repeated to form multiunit systems, independent of the scale of production. According to Palm et al. (2018), the range of aquaponic systems were categorized into (1) mini, (2) hobby, (3) domestic and backyard, (4) small/ semi-commercial and (5) large(r)-scale systems, as described below:
Fig. 7.5 Principle of a domestic coupled mini aquaponic system (\ 2 m<sup2/sup, after Palm et al. 2018) with aeration (a) and a pump (b), the hydroponics (c) act like a biofilter
Mini installations (Fig. 7.5) usually consist of a small fish reservoir such as a fish tank or aquarium on which the plants grow on the surface or within a small hydroponic bed. Conventional aquarium filters, aeration and pumps are usually used. Mini systems are usually 2 msup2/sup or less in size (Palm et al. 2018). These small aquaponic systems can be used in the home with only few plants for home consumption and planted with plants such as tomatoes, herbs or ornamentals. Such systems add new values to human living space by adding 'nature' back into the family life area which is especially popular in big cities. Some mini systems consist of only a plant vase and one or more fish without filter and pump. However, these systems are only short-term to operate because a regulated filtration is missing.
Fig. 7.6 Principle of a coupled domestic hobby aquaponic system (2—10 msup2/sup after Palm et al. 2018) with (a) fish tank and aeration, (b) sedimenter or clarifier altered after Nelson and Pade (2007), (c) hydroponics bed, e.g. gravel with different crops which acts like a biofilter and (d) a sump with the pump
Hobby aquaponic systems are categorized to reach a maximum size of 10 msup2/sup (Palm et al. 2018). With a higher fish stocking density, more feed and aeration, a mechanical sedimentation unit (sedimenter/clarifier) is necessary (Fig. 7.6). The sedimenter removes particulate matter —'sludge' such as faeces and uneaten feed from the system without using energy. The water flows by gravity from the fish tank to the sedimenter and then through the hydroponic tanks and then drops into a sump from where a pump or air lift pumps the water back to the fish tanks. In hobby installations, the plant beds act as a natural microbial filter and often media bed substrates such as sand, fine gravel or perlite are used. Hobby aquaponic systems are more the category of gimmicks that do not target food production. They rather enjoy the functionality of the integrated system. Hobby systems, as the name implies, are usually installed by hobbyists who are interested in growing a variety of aquatic organisms and plants for their own use and for 'fun'.
Domestic/backyard aquaponics has the purpose of external home use production of fish and plants characterized as having a maximum production area of 50 msup2/sup (Palm et al. 2018). These systems are built by enthusiasts. The construction is technically differentiated with a higher fish production, additional aeration and a higher feed input. The coupled aquaponics principle is applied with the use of one single pump which recirculates the water from a sump (lowest point) to higher standing fish tanks and then by gravity via sedimenter and a biofilter (with aeration and bacteria substrates) to the hydroponic units (Fig. 7.7).
Fig. 7.7 Principle of a coupled domestic backyard aquaponic system, 10—50 msup2/sup (from Palm et al. 2018) with (a) fish tank and aeration, (b) sedimenter or clarifier altered after Nelson and Pade (2007), (c) biofilter with substrates and aeration, (d) hydroponic unit which could consists of combined raft or DWC channels, (e) gravel or sand media substrate system, (f) nutrient film technique NFT-channels and (g) a sump with one pump
For biofiltration, conventional bed filters can also be used as described in Palm et al. (2014a, b, 2015). In backyard aquaponics, hydroponics could consist alone or together of raft or DWC (deep water culture) troughs, substrate subsystems such as coarse gravel/sand ebb and flow boxes or nutrient film technique (NFT) channels. In the northern hemisphere, in outside installations, production is limited to the spring, summer and early autumn periods because of the weather conditions. With this scale of operation, fish and plants can be produced for private consumption (and production can be extended through small greenhouse production), but direct sales in small quantities are also possible.
Small and semi-commercial scale aquaponic systems are characterized by being up to 100 msup2/sup (Palm et al. 2018) with production focused on the retail market. More tanks, often with a higher stocking density, additional filters and water treatment systems and a larger hydroponic area with more diverse designs characterize these systems.
Large(r)-scale commercial operations above 100 msup2/sup (Palm et al. 2018) and reaching many thousands of square metres reach the highest complexity and require careful planning of the water flow and treatment systems (Fig. 7.8). General components are multiple fish tanks, designed as intensive recirculation aquaculture systems (RAS), a water transfer point or a sump allowing water exchange between the fish and plants, and commercial plant production units (aquaponics s.s./s.l.). As fish production is meant for intensive stocking densities, components such as additional filtration with the help of drum filters, oxygen supply, UV light treatments for microbial control, automatic controlled feeding and computerization including automatic water quality control classify these systems.
These systems have a multiunit design capable of upscaling under fully closed water recirculation which also allows for staggered production, parallel cultivation of different plants that require different hydroponic subsystems and better control of the different units in the case of disease outbreak and plant pest control.