Aims. Developing effective methods for evaluation due to anthropogenic changes of aquatic ecosystems. Methods. Using cyto- and genotoxic methods for evaluating the quality of the water environment using test organisms fish, namely their blood cells. Results. The investigated samples of water obtained before and aftertreatment of nitrate with the use cytogenetic approaches have been shown changes in blood leukocyte formula fish Danio rerio (L.), and genetic changes by micronucleus test of blood cells – red blood cells. Conclusions. This method is short term, yet technically simple, versatile and important bioassays. Hematological parameters – definition of blood counts and micronucleus test in addition to the standardized methods can be used for an objective and comprehensive assessment of toxic pollutants.Keywords: hematological parameter, biotesting, cytotoxicity, water.
