One of the most interesting though little-known water ecosystems of Łęczyńsko-Włodawskie Lakeland is its small water bodies – ponds and wetland reservoirs. Three ponds and three wetland reservoirs were studied in 2008 and then again in 2012 and 2013 to examine their rotifer assemblages. While watching the changes occurring in the plankton during periods of 4 and 5 years, we were trying to find out which of the reservoirs were inhabited by more sustainable rotifer assemblages and which ecological qualities were more closely related to such sustainability. The results of the studies revealed different, though insignificant, variability in the ecological properties of planktonic rotifer assemblages, particularly in the ponds, as well as they suggested some relationship between the sustainability of planktonic assemblages and their species diversity.