Data about total soluble solids of the Beefsteak and Cherry tomato cultivars were significantly different among all genotypes. Data presented in Table 2 illustrated the similar trend of TSS among Cherry cultivar, but it was significantly higher than the group of Beefsteak tomatoes. In comparison between Beefsteak and the Cherry tomato comparatively higher total soluble solid was found in cv. Aria  while the minimum in cv. Grandy. Mavromatis et al.  reported that the values of the total soluble solid of different varieties fall in the range 2–4%, but the concentrations of total soluble solid  vary with the variety and ripening stages due to the breakdown of polysaccharides. Titratable acidity was statically analyzed  and it showed significant variation among the nine cultivars of tomato and its values ranged from 2.45 and 3.97 g/L. These results are consistent with the data reported by Romero-Rodriguez et al.,within the range of 2.9–4.4 g/L. Significantly more concentration of TA was calculated in Cherry cv. Cheramy  which was similar to cv. Nactar  and Beefsteak cv. Grandy. Ascorbic acid plays an important role in the human diet because it cures the chronic disease, stress and scurvy. Ascorbic Acid of Beefsteak and Cherry tomatoes showed significant differences at P ≤ 0.05 with a range of 15.48–23.24 mg/100 g. These values were supported to the outcome of Mavromatis et al.  and Chattopadhyay et al.. Data presented in Table 2 illustrated that the maximum AA concentration was found in the Cherry cv. Claree  followed by cv. Aria,Nactar,Cheramy  and the minimum in Beefsteak cv. Dirk. The overall comparison between Cherry and Beefsteak, maximum AA concentration was recorded in cv. Claree  and the minimum in cv. Dirk. 

A possible reason for the differences obtained in AA content for the same variety can be explained for the incidence of light in tomato at the end of harvest, temperature conditions during pre-harvest, stackable planters harvest time and post-harvest. The level of AA is higher at the time of maturity and then went down. The biochemical parameter of the Beefsteak and the Cherry tomatoes revealed significant differences among all cultivars. ‘Aria’ of the Cherry group showed the significantly higher amount of total sugar,reducing  and non-reducing sugar. The cultivars including Beefsteak group were shown the statistically lower concentration of total sugar, reducing and non-reducing sugar than that of the Cherry group. The indexes are used to evaluate the quality of the fruits and it showed relatively significant variation among the cultivar. The color indexes  were statistically similar in the Beefsteak cvs. Dirk, Grandy, Naram, Vernal and Sahel but lower than the Cherry group. Significantly more darkness and yellowness were seen in cv. Aria while redness observed in cv. Claree.For years the human population of our planet has tended to be concentrated in urban centres, which increases the demand for food in cities. This, together with the growing concern regarding environmental sustainability and food security, is leading to new and complementary forms of local and sustainable food production that are practised for domestic use or self-consumption in backyards, rooftops and communal vegetable gardens. This is especially interesting in more deprived areas for people with low resources. Although the volume of food produced with more sustainable farming methods, at the domestic level or by small peri-urban producers, has a very low contribution to the overall demand for food in large cities, there is a growing demand due to the quality of the products obtained and the concerns arising about sustainability in urban areas. In addition, maintaining food security and water scarcity have emerged as a critical challenge. Sustainable food production by saving and recycling water and nutrients is considered one of the possible solutions. This is, precisely, the basis of aquaponics, a biointegrated system that links aquaculture with hydroponics and is considered a model of sustainable food production,by taking advantage of wastewater from aquaculture and using it as nutrients for plant growth.

Domestic aquaponic systems are an option when it comes to producing food for self-consumption,contributing in improving food security and self-sufficiency, which in cities such as Sydney  could reach 15 %. They have the ability to adapt to being a form of peri-urban cultivation to produce various vegetables, such as leafy greens, which are considered part of a more balanced and healthy diet. This system also has a great potential for indoor food production regardless of climatic conditions. Hence, aquaponic production systems can be located on non-arable land close to markets, thus shortening the supply chain and reducing the carbon footprint associated with rural farms and transporting produce to city markets. It could also become an integrated agricultural system that plays a crucial role in future so-called “Smart cities”, especially from an environmental, socioeconomic and sustainable perspective, as it employs innovative systems to provide, through short supply chains, fresh food. Although there are no official censuses by countries of aquaponics facilities for domestic use or self-consumption,it seems to be an extended practice. One of the characteristics that make domestic aquaponic systems difficult to evaluate is that they are very heterogeneous, with a variety of designs adapted to the different socioeconomic and climatic conditions, also using different species of fish and polycultures of different vegetables. It is very difficult to find quantitative data on fish and vegetable polyculture production in these systems, or if one does, they do not appear to have been evaluated with a scientific procedure. Aquaponic systems with a tank size of 1000 L and a growth space of about 3 m2 can be considered micro-scale,and are suitable for domestic production for a family home, with the purpose of producing several vegetables and herbs at the same time for their subsistence. In the majority of cases, especially in commercial systems, only one crop and one fish species are produced at the same time. In micro-scale systems, producing a variety of crops  is most common, particularly when they are intended for selfconsumption. There are very few research works related to polyculture aquaponic systems and the existing ones include few species cultivated in them. However, aquaponic systems aimed to provide a healthy and complete diet to their users require the production of a high and varied number of vegetal species.

With this in mind, the main objective of this study was to assess an aquaponic production of more than 20 vegetables, fruits and herbs, together with a fish species, with a self-consumption purpose, in a marginal neighbourhood of the city of Seville,taking into account the climatic limitations during summer and winter. In this regard, operating an aquaponic system in locations subjected to low temperatures during some periods constitutes a challenge if fish species not adapted to these conditions are used. This sometimes leads to excessive energy consumption, which often represents one of the main costs of aquaponic production. Hence, it is important to define strategies to avoid having high energy costs and to achieve economic sustainability of this type of production. Therefore, as a specific objective, two methods were tested to avoid excessively low water temperatures in the fish tanks, in order to optimise the operation of the aquaponic systems in winter.The study was conducted in a greenhouse located at IES Joaquín Romero Murube secondary school in the Polígono Sur neighbourhood,which has one of the highest rates of social exclusion and economic poverty in Spain. The greenhouse, 9 m long, 5 m wide and 3.5 m high,had a clear plastic polyethylene film covering. The most extreme temperatures were reached in December and June. From June 21st to October 15th, the plastic cover of the roof of the greenhouse was replaced by a shading mesh  to avoid extreme high temperatures. Therefore, temperatures during these months did not exceed 40 ◦C. Two identical self-constructed aquaponic facilities were built based on FAO designs for micro-scale aquaponic systems,with some changes made to improve the performance and handling of the facility. Cheap and easy-to-obtain materials were employed. The total investment costs for the construction of the facilities were estimated to be around 1300 € for each of the MAS.

Each of the MAS consisted of a tank for the fish production and a conjunction of three different hydroponic sub-systems:Nutrient Film Technique,Grow Bed  and Deep Water Culture. In each MAS,stackable flower pots the total cropping area was 4.56 m2,of which 3 m2 correspond to NFT, 1.2 m2 to GB and 0.36 m2 to DWC. The total volume of recirculating water was 1.8 m3. The fish tank consisted of an IBC  type tank  with a 0.7 m by 0.7 m opening trimmed on top to allow the operations with the fish. Two meshes were placed on the opening, one to avoid the fish jumping out of the tank and another to shade. A correct level of dissolved oxygen in the water inside the tanks was ensured by means of a 5 w air pump with a flow of 0.48m3 h− 1. The water in the tank was maintained with a constant level in order to always ensure the same volume. The fish tank was connected through a 50 mm PVC pipe to another 0.45 m3 tank acting as a clarifier, in order to avoid anaerobic conditions due to an excessive accumulation of solids. This tank had a cylindricalconical shape with a drain valve at its bottom. The water from the fish tank entered the clarifier through an elbow, causing a circular motion which facilitated the sedimentation of solid waste, while the clean water flowed upwards. Water came out of the clarifier through a 75 mm PVC tube attached to a bulkhead connector located 9 cm below the top edge and passed to the top of the grow bed tank. This was made with an IBC tank cut in half with a capacity of 0.45 m3 filled with 0.4 m3 of prewashed expanded clay. This tank acted at the same time as a bacterial bio-filter and as a GB hydroponic sub-system. From there, the water passed through a bell syphon to the sump tank,containing 0.54m3 of water. A 0.04 m thick extruded polystyrene foam sheet  covered 1/3 of its surface, and three holes  allowed placing plants inside it, separated 0.25 m from each other. From the sump, 80 % of the water was sent back to the fish tank thanks to a submersible SunSun JTP 4800Lh− 1 and 32 w pump. The remaining 20 % was recirculated by an NFT hydroponic sub-system, and back to the sump again. For the NFT, five PVC pipes,placed on concrete blocks levelled to obtain a slope of 1%, were used. Each of the pipes had 12 holes with a diameter of 0.05 m at 0.25 m from each other.A total of 22 crops were grown during a year in both MAS. A polyculture of fruits, vegetables and herbs was selected  with the objective of providing a family with a diversity of products that enabled achieving a nutritionally healthy diet.

The species used were: Raf tomato,Roma tomato,Water melon,Eggplant,Cucumber,Italian frying, Lamuyo and Goat horn pepper,Basil,Onion,Stevia, Pumpkin,Melon,Chard,Broccoli,Cauliflower,Cabbage,Chinese cabbage,Strawberry,Potato,Zucchini,Lettuce. The different species were planted according to their optimal growing season and the seedlings were obtained from commercial plant nurseries. These seedlings were selected with at least four true leaves and approximately one month after germination. For planting, the root system of the seedlings was carefully washed and inserted in the corresponding hydroponic subsystem. For each species, the different maintenance tasks usually used in their hydroponic production  were performed.Before starting the aquaponic production, water was recirculated through the MAS during 40 days without fishes or plants, so the nitrifying bacteria could proliferate. For the initial loading of both MAS, a mixture of rainwater and drinking water from the public network was employed to achieve a pH between 7 and 7.4. After that, only dechlorinated water coming from the public network was used to replenish water losses by direct evaporation and evapotranspiration. The MAS were monitored throughout a complete year from April 24th, 2018 to April 24th, 2019. Management and maintenance actions were carried out in the same way as a family would do for a self-managed aquaponic production. An electricity meter was installed in each of the systems to record consumption.