Water and bottom sediment samples collected from a few fish-breeding ponds/reservoirs were subjected to tests. The aim of this paper was to determine the total content of aluminium and its fractions in the samples tested to estimate the potential risk to fish caused by the toxic forms of aluminium. The monomeric inorganic aluminium in waters was determined using the ion exchange and extraction-colorimetric method with oxychinoline according to Barnes's-Driscoll's procedure. The bottoms were fractionated using a three-step sequential extraction procedure and the microwave mineralisation. The total content of aluminium in waters and extracts was determined using the spectrophotometric method with eriochromocyanine R, and comparatively using the ICP OES technique. The results were subjected to statistical analysis. The level of concentration of labile Al in the waters about 26-34 μg/dm3 and content of exchangeable Al 5-34 mg/g range in bottom sediments are possibly hazardous to aquatic organisms.