The study on the structure of the rotifer and crustacean communities of a polihumic dystrophic water body was made with respect to specific physical-chemical and biological parameters connected with the lack of fish predation. Within the whole examination period only invertebrate predation was observed with a high participation of Chaoborus larvae, which probably structured the plankton assemblages. There were 88 zooplankton species identified, with rotifers dominating. The summer months were taxonomically the richest, while winter was the poorest. With regard to the zooplankton densities the dominance of rotifers over crustaceans was recorded. The highest numbers of individuals were noticed in the spring-summer season, while the lowest in the winter. A high participation of ‘pond’ and acidophilic forms was found.