The aim of the study was to estimate the effect of culture conditions and culture siteon magnesium (Mg) and zinc (Zn) concentrations in freshwater fish. The study encompasseddorsal muscles in five fish species: common carp (Cyprinus carpio L.), rainbow trout (Oncorhynchus mykiss Walbaum) and Siberian sturgeon (Acipenser baeri Brandt), northernpike (Esox lucius L.) and grass carp (Ctenopharyngodon idella Valenciennes).A total of 125 fish comprised 25 individuals of each species, aged from 6, 9, and 12 months. The fish were cultured in privately owned fish breeding ponds (Western Pomerania, Poland). For chemical and biochemical assays, samples of dorsal muscles were takenfrom each fish. Tissue samples were wet mineralised in concentrated HNO3 in a CEMMDS 2000 microwave oven. Magnesium and zinc concentrations were determined by inductivelycoupled plasma atomic emission spectrometry (ICP-MS) in a Jobin Yvon type JY-24 apparatus. The pursuit of the research we had an approval of the Polish Local EthicsCommittee nr 9/05. The magnesium concentration in the dorsal muscles ranged from95.3÷347.6 mg kg–1 w.w. The highest Mg concentration was found in rainbow trout (347.6±32.2 mg kg–1 w.w.), and the lowest in grass carp (95.3±11.3 mg kg–1 w.w.). Zincconcentration varied from 6.7÷98.8 mg kg–1 w.w. The highest was found in the muscles ofSiberian sturgeon (98.8±0.4 mg kg–1 w.w.), and the lowest in rainbow trout (6.7±0.7 mg kg–1 w.w.). It was found that the breeding place significantly affected the Zn and Mg concentrationsin the muscle tissue among individual freshwater fish species. The magnesiumand zinc concentrations were also significantly affected by the type of feed.