Bioassay methods recently become leading in determining water quality. With reactions of living organisms (test objects) one can state water toxic effects on an organism. Indicator of living organisms state is the efficiency of physiological processes that ensure its normal development. Using information-measuring systems in animals (crawfishes, crabs, surfs) these figures have been recorded. Rapidness and possibility of integrated assessment of contaminants impact on biota is the advantage of this method, it can be used as a method of water toxicity early detection.