## 1 Introduction  
Aquaculture is a sector of food production that has experienced the greatest growth worldwide thanks to scientific progress and technological innovation, providing high-quality proteins and fats, and helping achieve sustainable development goals [1]. These foods are needed to provide a healthy and nutritious diet for an ever-growing population. However, some production techniques can lead to conditions that cause fish to acquire undesirable flavors and odors, commonly referred to as 'off-flavors' [2]. This problem affects freshwater species in particular, such as rainbow trout (_Oncorhynchus mykiss_), tilapia (_Oreochromis niloticus_ and _O. aureus_), largemouth bass (_Microperus salmonoides_), Atlantic salmon (_Salmo salar_), tench (_Tinca tinca_), and others [3] grown in recirculation aquaculture systems (RAS), ponds, cages, and other culture systems. Tench (_Tinca tinca L._, 1758) is a freshwater cyprinid fish species of Eurasian origin [4]. Its distribution is worldwide, and due to human-mediated translocations [5], it is currently established on every continent except Antarctica [6]. It is an important gastronomic and angling fish, highly valued in local regions of Spain and Italy as well as in European countries such as Poland, Germany, and the Czech Republic [7], although production in 2022 did not reach 700 tons in Europe and barely exceeded 14 tons in Spain [8]. This species is considered one of the best candidates for the diversification of freshwater aquaculture in Europe because it is a traditional crop with high consumer demand and a high market price (between EUR 16 and 18 per kg\({}^{-1}\)) [8]. In addition, it has important natural and cultural value since it has been traditionally reared in extensive monoculture natural ponds frequently associated with other uses of water related to agricultural or livestock purposes [9]. Freshwater species, such as tench or even rainbow trout, live in shallow areas of lakes and ponds, preferring muddy or sandy substrates with submerged vegetation that favors their reproduction [10]. These species are consequently marketed with unpleasant odors and flavors brought about by certain VOCs caused by their environment [3]. Although water recirculation systems are established in aquaculture, they are affected by the presence of phosphorus, micronutrients, and organic matter, which can affect the water quality. These compounds are linked to the growth in phytoplankton that can produce secondary metabolites responsible for off-flavor characteristics in fish but have no negative impacts on human health [11]. Researchers have shown derivatives of alga, fungi, cyanobacteria, and microorganisms such as _Actinomycetes_ and _Myxococcus_ to play a role in the synthesis of secondary metabolites that are responsible for the unpleasant odor, taste, and color of the final product. The main sensory attributes in aquaculture fish are described as earthy, muddy, or moldy [11], and the primary contributors to these abnormal aromas are terpenoids, carotenoid derivatives, fatty acids, and sulfur compounds [12; 13]. Off-flavor aromas resulting from VOCs include 2-methylisoborneol, geosmin, 2-isopropyl-3 methoxyurazine, and 2-isobutyl-3-methoxypyrazine [14]. Geosmin and 2-methylisoborneol, in particular, are responsible for unpleasant odors in rainbow trout, tilapia, Arctic charr, largemouth bass, and Atlantic salmon [15]. Therefore, marketing fish with unpleasant flavors and odors has significant commercial implications. Lippohilic compounds are removed via passive diffusion through the gills or skin, or through the metabolism of the fish, before they are excreted; however, the relative importance of these processes is unknown [2]. There are various techniques for removing the concentration of off-flavor compounds. Some focus on preventing their occurrence by controlling aquatic microorganisms in the culture water by applying ozone or algaecides [2].