An analysis of environmental threats showed that the complete influence of shale gas production on the environment is bigger than in the case of gas production from a traditional oilfield. Hydraulic fracturing of shale, done on a much larger scale, results in huge amounts of liquid waste that must be managed in a rational way. An optimum solution to this problem is reusing flowback water to develop fluids for later fracturing. This article discusses the composition of the fluids used in hydraulic fracturing of non-conventional deposits as well as the flowback water. In the case of the examined liquids, toxicological tests have been carried out using microbiotests of ToxKit types Microtox, MARA, Daphtoxkit F magna, and Thamnotoxkit F. The research was done on a sample of fluids for hydraulic fracturing, and on flowback water obtained in hydraulic fracturing of shale formations in Poland. The tests are essential for correctly managing flowback waters after fracturing.