Studies on the occurrence of aquatic microorganisms in the newest water reservoir Zarzeczany village were carried out in years 2001-2004. Hydro chemical analysis was performed using standard methods. Bait method was used to isolate the fungi. In the reservoir 52 fungi species were identified: fish pathogenic Achlya debaryana, A. polyandra, Aphanomyces laevis, Dictyuchus monosporus, D. sterile, Saprolegnia ferax, S. monoica, S. parasitica, human pathogenic Candida albicans, C. tropicalis and Trichosporon cutaneum, decomposing keratin Blastocladiopsis parva, Catenaria anguillulae, C. verrucosa, Catenophlyctis variabilis, Lagenidium humanum, Rhizophydium keratinophilum, and decomposing chitin Aphanomyces astaci, Karlingia chitinophila, Rhizidium chitinophilum, Asterophlyctis irregularis and Blastocladiella brytanica.