Nitrate pollution in freshwater has become an increasing concern for both environmental sustainability and human health, especially in water reuse systems and intensive aquaculture. Photocatalytic reduction in nitrate to nitrogen gas (N₂) represents a promising low-chemical treatment strategy that can operate under sunlight or LED irradiation, and in general, enable nitrate removal without generating concentrated waste streams. Over the past decade, the development of advanced photocatalytic materials, including heterojunction semiconductors, plasmonic catalysts, and single-atom co-catalysts, has significantly enhanced visible-light absorption and overall photocatalytic performance. Despite these advances in photocatalyst design and synthesis, several critical challenges still limit the large-scale implementation of photocatalytic nitrate reduction to N₂. First, selectivity toward N₂ remains limited, as competing reaction pathways often lead to the formation of undesirable byproducts, such as nitrite (NO₂⁻), ammonium (NH₄⁺), and nitrous oxide (N₂O). Second, nitrogen reaction pathways are often uncertain, because many studies lack isotopic labeling or nitrogen mass balances, making it difficult to verify that the detected N₂ originates from nitrate reduction. Third, practical implementation is restricted by several technical challenges, including catalyst fouling or leaching, limitations in reactor design, excessive addition of hole scavengers, and the relatively high energy demand associated with indoor LED-driven systems. This review critically surveys advances from 2015 to 2025 in photocatalytic materials and reaction mechanisms for nitrate conversion to N₂. It highlights best practices for reliable product quantification and reaction pathway validation, and evaluates the feasibility of integrating these systems into recirculating aquaculture systems (RAS), where effective nitrate management is essential. In addition, the potential role of modern inline nitrate sensors (optical and electrochemical) and automated process control is discussed, outlining pathways toward hybrid photocatalytic–biological nitrate removal systems for sustainable aquaculture applications.

Although the ichthyofauna of Serbia consists of over 100 species of fish, 32 of them are recognized as allochthonous species. Allochthonous and invasive species pose a significant problem for the native fish fauna and entire ecosystems. The black amur was first recorded in Serbia in 2022 in the Danube within the Đerdap National Park, and in 2023, the find was confirmed over 300 km upstream, in the Danube near Gložan (1280 rkm). The cultivation of black amur in the countries of the region, combined with its invasive potential and a wide range of potential habitats in the Danube basin, create a high risk of invasion of this species

Research of fish communities was carried out in November 2023 in artificial lakes in the area of Bela Crkva. Using a multiparameter probe, the basic physical and chemical parameters of water quality were measured, according to which the waters of these lakes belongs to the class I and II waters. In total, the presence of nine species from six families was registered. Of the total number of registered species, two are listed in the Berne Convention, while one species is listed in the Habitats Directive. According to national legislation, one species is strictly protected, while three species are protected. It can be concluded that the biological diversity of the ichthyofauna of the studied lakes is solid, and that the basic characteristic of the ichthyofauna is a high level of autochthonousness.

Ovim saopštenjem analizirane su naznake biotičke homogenizacije u akumulacijama Sot, Moharač, Bruja i Međeš na osnovu monitoringa iz 2016, 2019, 2022. i 2025. godine. Rezultati ukazuju na ponavljanje dominantnih fitoplanktonskih grupa, pojednostavljenje makrozoobentosa i smanjenje broja ribljih vrsta. Uočeni obrasci ne predstavljaju direktan dokaz homogenizacije, ali ukazuju na trend konvergencije zajednica i potrebu za detaljnijim kvantitativnim i kvalitativnim analizama.

The Ponjavica River, as the central hydrological feature of the eponymous Nature Park, has been subject to long-term monitoring aimed at assessing the ecological status of its fishing waters. This study analyzes physicochemical parameters, phytoplankton structure, and macrozoobenthos from 2017 to 2024. Although functional reclassification of the river is needed, the results indicate a persistently degraded ecological status, with frequent cyanobacterial dominance. The macrozoobenthic community is reduced and composed predominantly of tolerant taxa.