Aromatic herbs are plants whose fresh, dried or dehydrated leaves are used as essence, spice, for medicinal purposes, processed or as infusions that are in high demand in developed countries; therefore, they have a high potential for the export market. Globally, aromatic herbs in culinary use are becoming more important because consumers have a desire for healthier foods, with a significant increase in the choice of organic foods and the rise in ethnic foods (Makri & Kintzios, 2007). Among the herbs with strong demand in the market are basil (Ba; Ocimum basilicum L.) (Pérez-Rostro, Hernández-Vergara & Ronzón-Ortega, 2012), spearmint (Sp; Mentha spicata L.) and peppermint (Pe; Mentha piperita L.) (Dzida, 2010; Nelson, 2005). Some of these species have also been used as medicine due to their antiseptic properties, eg M. spicata is a natural repellent for Anopheles stephensi, the malaria vector and it acts as antimutagenic with effects on reproductive biology in humans (Iannacone & Alvariño, 2007). With these features, aromatic plants create a business opportunity for producers in developed countries who are able to produce them with high quality and the ability to meet demanding markets (Sánchez & Lucero, 2012) under organic production systems such as aquaponics (Blidariu & Grozea, 2011).

Aquaponics is the integration of hydroponics with recirculating aquaculture system (Rakocy & Hargreaves, 1993). This technique has been proposed as a sustainable alternative for an efficient use of water and to reduce the environmental impact associated with agricultural production (Adler, Harper, Wade, Takeda & Summerfelt, 2000; Ramírez, Sabogal, Jimenez & Hurtado, 2008). Overall, aquaponics is a comprehensive production system in which waste, synthesized by an aquatic organism (usually fish), is converted by bacterial action into nitrates, which serve as a nutrient source for plants (Rakocy, 2010; Zhang et al., 2011). The biological principle is based on the required mineral nutrients for plant growth and development such as nitrogen and phosphorus, which are produced as waste by fish. Uneaten food and animal excretion free ammonia in water, which is converted by bacterial action in these nitrites and nitrates. Subsequently, plants work as biological water filters and take what they need from water, and so, absorbing these nitrates, they clean the liquid which returns to fish, allowing the latter to live in a suitable environment for growth and development (Rakocy, 2010). In this sense, there has been an increase in crop production in response to high concentrations of nutrients derived from microbial decomposition observed in aquaponic systems (Pérez-Rostro et al., 2012). This is due to the ability of plants to absorb and store nitrates, which are a product of fish waste ( Blidariu & Grozea, 2011). All these lead to the production of food without the external addition of chemicals, fertilizers and, therefore, aquaponics can be considered as organic farming (Al-Hafedh, Alam & Salaheldin, 2008).

Basil, spearmint, and peppermint may be very useful as biological filters in aquaponic systems to absorb and prevent the accumulation of nutrients produced by fish excreta (Rakocy, 2010). On the one hand, production of herbaceous plants in aquaponic systems can be considered as an alternative sustainable production that increases incomes and mitigate the conventional aquaculture production systems environmental impact. On the other hand, they can produce different fish species for human consumption coupled with the production of commercially used plants, which increases its production value (Graber & Junge, 2009). However, it is remarkable the shortage of information on the herbaceous production in aquaponic systems, particularly peppermint and mint, which are plants with productive potential in such systems (Bakiu & Shehu 2014; Campos-Pulido, Alonso-López, Avalos-de la Cruz, Asiain-Hoyos & Reta-Mendiola, 2013; Espinosa et al., 2016). Therefore, the aim of this study was to evaluate the growth and development of basil, spearmint and peppermint as part of the biological filter in aquaponics with tilapia.

According to the results, the pond’s water physicochemical parameters were observed within the optimal range for tilapia (Diario Oficial de la Federación [DOF], 2012), showing the system’s biological maturity. This suggests that it is possible to integrate this freshwater species culture with the production of the evaluated herbaceous. Meanwhile, the temperature recorded at the HB values were slightly outside the optimum range considering that water temperature in the aquaponic system must be maintained between 21.1 °C and 23.8 °C, suitable for plant growth (Nelson, 2008; Rakocy, 2010) because higher temperatures can cause reduced growth and susceptibility to pathogens (Nelson, 2005; 2008). However, during the experimental period no signs of disease were observed in plants. The pH range (7.80 - 8.30) was considered high. The pH is a key factor for plant growth because it affects the nutrients absorption capacity available in water and, thus, their development (Karimaei, Massiha & Mogaddam, 2004; Rakocy, Shultz, Bailey & Thoman, 2004). As reported by Caló (2011), ideally pH should be maintained between 5.5 - 6.5, so that plants achieve greater nutrients absorption. Literature suggests that the temperature out of range coupled with a high pH can cause growth problems in plants (Rakocy, 2010). However, no abnormalities were detected in any herbaceous that may have been related to lack of nutrients. This shows that the assessed species are able to adapt to the physicochemical conditions that may occur in aquaponic systems. OD values observed in the HB water are considered optimal for the plants. According to Nelson (2008) and Rakocy (2010), it is extremely important to maintain high OD level (close to 80% saturation) due to various factors such as fish respiration, the oxidation process of nitrifying bacteria, and oxygen absorption by the root region of plants which, added to the high organic loads produced, consume considerable amounts of oxygen in the chemical transformation processes in these systems (Rakocy, 2010).

EC was recorded in multiple levels recommended for aquaponic systems: 0.3 dS/m³ - 0.8 dS/m³ (0300 mS/m³ - 0800 mS/cm³) (Nelson, 2008), 0.3 dS/m³ - 0.6 dS/m³ (0300 dS/m³ - 0600 mS/cm³) (Rakocy et al., 2004, Rakocy, 2010) 0.51 dS/m³ to 0.54 dS/m³ (0510 mS/m³ - 0540 mS/cm³) (Roosta & Hamidpour, 2011); although Nelson (2008) considers these values to be lower than the recommended range for optimal plant growth and development if it were a hydroponic system. Such EC difference recommended for hydroponics and aquaponics is attributed to two factors: a) the nutrients in aquaponics are generated constantly (Rakocy, 2010), and b) the organic nature of the nutrients low concentrations of salts is generated, hence low conductivity values (Nelson, 2008). Based on the above, it is considered that the EC values observed indicate the good concentration of nutrients available in water, which were efficiently utilized by plants even when roots were in a medium with slightly alkaline pH, showing that used herbaceous adapt to such systems. A key point to consider is that aquaponic systems require some time to balance their physicochemical parameters and this stability is directly associated with the maturity of their biological filters (Caló, 2011) and the load of beneficial nitrifying bacteria.

The recorded height of the evaluated plants in this study is compared with observed data in hydroponics (Pérez-Rostro et al., 2012) and even with greater heights as in the case of Pe. In the case of Ba, the recorded height and SLA values were lower compared to hydroponic plantations under experimental conditions (González, Rodríguez, Sánchez & Gaytán, 2009) and higher compared with the reported production by Carrasco, Ramírez & Vogel (2007) in hydroponic systems with Nutrient Film Technique (NFT). The lower values of height and specific leaf area observed in the present study may indicate a deficit of nutrients in the aquaculture effluents whose concentration is controlled in hydroponics by managing nutrient solutions. The highest values are possible due to the increased colonization of biological filters by bacteria that constantly transform ammonium and nitrite into nitrates, essential for plant nutrition (Pérez-Rostro et al., 2012) due to the presence of river gravel in HB, compared to using NFT. Spearmint showed the best adaptive response, at the end of the experimental period with greater leaves number developed and a greater weight gain per day (AGR), similar to that observed by Salam, Prodhan, Sayem & Islam (2014) who considers such plants to be highly profitable for aquaponic raft systems. Furthermore, the results suggest that plants can achieve greater development in aquaponic systems if the culture period extends (Campos-Pulido et al., 2013), which would result in greater crop production compared with conventional crop systems. In this sense, it is necessary to analyze how growth factors (temperature and nutrient concentrations) in aquaponic systems affect plants in order to assess their effect on economically important properties as it has been observed that the aquaponic influences the amount of fruit and flavor (Graber & Junge, 2009) that are not always positive, so there must have a control of the water physicochemical parameters according to the plant culture needs (Campos-Pulido et al., 2013).

Such observed productivity in Sp, suggests that this herb growth is favored by the aquaponic systems, compared to traditional cultivation (Campos-Pulido et al., 2013). However, Ba production obtained in experimental systems is considered high compared with the reported by Carrasco et al. (2007) and for the production of Pe. According to the literature, this study would be the first report for this species grown in aquaponics.

Growth and FCR recorded data suggest that fish that consumed and used the supplied food presented a rapid and remarkable growth and development, resulting in a proper final biomass production and a harvest of healthy organisms. Based on the fish, growth is directly related to metabolism, environment, the offered conditions and that ratio may vary within the same area, with time and from one specimen to another (Enberg, Dunlop & Jørgensen, 2008). Given the above, it was considered that the planted fish density in each pond was right because, as noted, two basic conditions were met: 1) fish were healthy and therefore a high survival rate was achieved (almost 100% of organisms); moreover, during the experimental period fish showed no disease in the skin, eyes or gills and at the end of the experiment the growth of each organism was considerable, and 2) by maintaining full tilapia culture is possible to obtain sufficient amount of metabolic waste that then go through the process of bacterial decomposition with the consequent production of nutritive elements for plants in this way, cleaning the recirculating water.

If these elements are not removed, they may reach toxic levels for fish, but in aquaponic systems they fucntion as liquid fertilizer (mainly nitrates) for plants which, in turn, act as a natural pond water filters and hydroponic beds (Mateus, 2009). Thereby, this allows the survival of fish and shows that it is possible to integrate the production of this freshwater species with the evaluated herbaceous crops.

The plants studied here act as biological filters (Espinosa et al., 2016), being particularly important the role played by Sp since the data suggest an increased production in biologically mature aquaponic systems compared to the traditional production systems (Caló, 2011; Campos-Pulido et al., 2013). In aquaponics, some productivity aspects in herbaceous are unknown, as the essential oils content are known to be strongly influenced by the environment (Tabatabaie & Nazari, 2007) and which are economically important (Telci et al., 2011). Therefore, information on management aquaponic system and the results presented here are important bases that can be used to establish future studies on the evaluated herbaceous. Although tilapia did not present diseases caused by poor water quality, it is considered important to continue these studies, particularly on those factors affecting the welfare and animal health and on the quality of plants obtained in aquaponic systems.

The use of evaluated herbaceous in biological filters in aquaponic systems for intensive production of tilapia is feasible; as basil, mint, and spearmint suit aquaponic farming conditions. Nutrients from excreta and uneaten food decomposition are found in adequate concentrations and assimilable chemical form, which resulted in plant growth, biomass production and 100% survival of organisms. Water quality was kept in acceptable ranges for both tilapia and herbaceous production. It was considered important to conduct studies on hydraulic retention rate in HB, biomass balance (plant and animal) as well as vegetables nutritional and nitrates values obtained in aquaponic systems to establish whether or not they meet the commercial standards and innocuousness for organic farming.