## 1 Introduction  
The world's population has grown rapidly in the last century, and is predicted to reach 10 billion by 2050 [1, 2]. This rapid population growth severely strains natural resources, including plants, water, and land. These resources are already overexploited [3, 4, 5]. Anthropogenic factors, including conventional agricultural practices, are significant drivers of environmental degradation [2]. Traditional (soil-based) cultivation is often associated with high inputs of heavy inorganic fertilizers, synthetic pesticides, and water [6]. Lately, there has been an appreciation of the need to adopt environmentally friendly crop cultivation methods to mitigate environmental degradation. Aquaponics and hydroponics are increasingly used to cultivate vegetables; however, using these systems to grow medicinal plants is novel. Both cultivation technologies could limit the exploitation of some endangered medicinal plants from the wild, reduce water wastage during crop cultivation, and enhance the commercialization of medicinal plants [7]. Cultivating fish and medicinal plants in aquaponics is feasible and ecologically friendly, and integrates hydroponics and aquaculture. Aquaponics is regarded as one of the most resource-efficient production systems [8], where wastewater is recycled and reused, minimizing contamination of adjacent water bodies [9]. In hydroponics, another type of soilless cultivation, plants are grown in a sterile nutrient solution (water culture) and inert substrate [10]. Cultivating medicinal plants under precise and controlled environmental conditions in a hydroponic system improves quality, bioactivity, and biomass output on a commercial scale [11; 12]. This approach is beneficial in areas with persistent environmental stresses, such as extreme cold, heat, and drought [11]. The prospect of using these cultivation systems to optimize the synthesis of secondary metabolites in highly valued medicinal plants is enticing [13; 14]. Secondary metabolites produced by plants play a crucial role in plants' defense, protection, and signaling systems [15]. Notably, many of the secondary metabolites produced by plants are valuable to the pharmaceutical industry [16]. Some bioactive compounds have pharmacological or toxicological effects on humans and animals [17]. Some plant-based compounds have cosmetics and nutritional uses; they produce drugs, dyes, fragrances, and dietary supplements [18]. Plant pathogens and predatory insects have been successfully controlled using plant extracts with high bioactive secondary metabolite contents [19; 20; 21]. Therefore, developing cultivation protocols to optimize the secondary metabolite content, and thus, the medicinal value of plants, is certainly a worthy research venture. _Helichrysum odoratissimum_ ([PERSON] belongs to the Asteraceae family, and is a spreading perennial shrub with linear, oblong leaves that are greyish-white and woolly on both sides [22]. The flowers are pale golden yellow, with tiny flower heads borne in clusters at the terminals of the branches, woody at the base, erect, and up to 50 cm high, and bloom all year [23]. It is an aromatic species, and it is widely distributed throughout intertropical and Southern Africa [24]. _Helichrysum odoratissimum_ is one of the most harvested and traded plants in South Africa [22]. Many studies have validated its traditional uses in traditional medicinal treatment of abdominal pains, heartburn, fever, catarrh, headache, menstrual problems, urinary tract infections, and wounds [22; 24]. Numerous compounds, including chalcone, helichrysetin, 3,5-dihydroxy-6,7,8-trimethoxy flavone, 3-0-methylquercetin, and 3\({}^{\prime}\)4\({}^{\prime}\)3,5-tetrahydroxy-7-methoxyflavone, are found in the flowers of _H. odoratissimum_[24; 25]. The crude extracts and isolated compounds from _H. odoratissimum_ exhibit pharmacological effects such as antibacterial, antimycobacterial [26; 27], antifungal [22; 27; 28; 29; 30], anti-inflammatory [31], and antioxidant [26] effects, as well as cytotoxicity and toxicity [32].