Terech-Majewska E., Pajdak J., Siwicki A.K. 2016. Water as a source of macro- nutrients and micronutrients for fsh, with special emphasis on the nutritional requirements of two fsh species: the common carp (Cyprinus carpio) and the rainbow trout (Oncorhynchus mykiss). J. Elem., 21(3): 947-961. DOI: 10.5601/ jelem.2015.20.4.940 Journal of Elementology ISSN 1644-2296 REVIEW PAPERS WATER AS A SOURCE OF MACRONUTRIENTS AND MICRONUTRIENTS FOR FISH, WITH SPECIAL EMPHASIS ON THE NUTRITIONAL REQUIREMENTS OF TWO FISH SPECIES: THE COMMON CARP (CYPRINUS CARPIO) AND THE RAINBOW TROUT (ONCORHYNCHUS MYKISS) Elżbieta Terech-Majewska 1 , Joanna Pajdak 1 , Andrzej K. Siwicki 2 1 Chair of Epizootiology University of Warmia and Mazury in Olsztyn 2 Department of Pathology and Immunology National Inland Fisheries Institute, Zabieniec near Warsaw AbstrAct In contrast to terrestrial animals, fsh can ingest minerals from food or directly from water. Although micro- and macro-elements are needed in small quantities, they play a key role in many metabolic processes. Trace mineral and macromineral defciencies may go unnoticed due to an absence of clear clinical symptoms in fsh. Absorption processes are determined by various factors, mostly mineral concentrations in water but also other water parameters. The required dietary supplementation of macronutrients and micronutrients is very diffcult to determine, and the amount of nutrients absorbed by fsh from water is equally diffcult to measure. Interac- tions between elements should also be taken into consideration. Many authors emphasize that phosphates may reduce the absorption of most micronutrients. Also, the current parameters of the water can affect the bioavailability. Some elements such as calcium, chlorine and sodium can be absorbed from ambient water in a quantity suffcient to meet the demand for this ele- ment. Other elements, however, require supplementation in a diet. For example, studies indica- te the need for supplementation of phosphorus, zinc, copper and manganese. Most research concentrates on feedstuff as a source of micro- and macronutrients. Meanwhile, information dr Elżbieta Terech-Majewska, Chair of Epizootiology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, 10-719 Olsztyn, Poland, e-mail: etam@uwm.edu.pl