This work describes the occurrence and blooming of some Cyanobacteria in an artificial, oligosaline, alkaline, microaccumulation in Serbia, which was formed on salines in 1963-64, and rehabilitated in 2009-10. The appearance and specific blooming of species common for tropical regions in Aleksandrovac Lake (N 42º29’22”, E 21º53’54”) before reconstruction (Cylindrospermum stagnale (Kützing) ex Bornet et Flahault, Synechococcus lividus Copeland, Chrysosporum bergii (Ostenfeld) Zapomělová et al., Anabaenopsis elenkinii Miller, Lyngbya aestuarii (Mertens) Liebman ex Gomont) and after reconstruction (Cylindrospermopsis raciborskii (Woloszińska) Seenayya et Subba Raju, Chrysosporum bergii, Anabaenopsis elenkinii, as well as Glaucospira sp. Lagerheim) was recorded for the first time in Serbia. The work also demonstrates the potential hazard to the environment (fishkill) due to the presence of specific blooming of Cyanobacteria. Alkaline salt ponds and lakes with extreme ecological conditions are places suitable for the development of alien and potentially invasive species.