Lakes Nemi (IT) and Beliansky tajch (SR) are heavily influenced by anthropogenic activity, which created suitable conditions for the expansion of invasive cyanobacteria and algae, such as Planktothrix rubescens. These cyanobacteria produce toxins called microcystins that negatively affect ecosystems. By analyzing the physico-chemical and microbiological indicators of surface water quality in these water objects, we examined the conditions under which P rubescens was able to expand.In the Nemi lake, the limit for pH set by Government Regulation No. 269/2010 Z.z 6,5 – 8,5. was exceeded. physical-chemical indicators in the Beliansky tajch were measured and result did not exceed the norm. By microbiological analysis we found that in the lake Nemi limits for coliforms, enterococci and cultivable bacteria at 22 ° C, STN EN ISO 6222: 2001 were exceeded. Microbiological indicators in the Beliansky tajch did not exceed the Slovak Government Decree no. 87/2008 Z.z. on requirements for natural swimming pools and the Slovak Government Regulation no. 269/2010 Z.z. for surface water quality. Microscopic analysis confirmed the occurrence of Planktothrix rubescens in both water bodies. Ferric bacteria have only been observed in Beliansky tajch, suggesting iron or manganese pollution. Mainly observed ferric bacteria was Gallionella sp., Leptothrix sp. was found in lesser quantities. Ecotoxicological test of Beliansky tajch with Daphnia magna and its immobilization was negative - less than 50% were immobilized, STN EN ISO 6341. 2013. Ecotoxicological test of Beliansky tajch with Lemna minor was positive, because average growth inhibition was above 30%, STN EN ISO 20079. 2008. 2008-07. After we repeated 3 times MALDI-TOF MS analysis of the sample from Beliansky tajch, on pure culture from TSA agar, we probably identified Pseudomonas geniculata.