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One of the most interesting and relatively little known water ecosystems of "Lasy Janowskie" Landscape Park is a group of old ponds which have been excluded from intensive fi sheries for many decades. Two of these ponds, belonging to pond complexes, and two other situated outside such complexes were studied in 1996, 2005, 2013 and 2015, regarding their planktonic rotifer assemblages. The total of 65 rotifer taxa were recorded in the plankton. The number of its species in individual reservoirs and years of study ranged from 7 to 21, and their density was from 29 to 775 ind. dm -3 . As many as 25 species in individual ponds and study periods represented dominnats. The present work aimed at determining which of those tiny yet fl oristically rich ponds were inhabited by more sustainable rotifer assemblages, regarding both their quality and quantity, and to which ecological qualities was such sustainability related to a higher degree; species richness, their diversity, density, biomass, composition or domination structure.. The results of the studies revealed slight variability of ecological properties among the planktonic rorifers in the ponds composing large reservoir groups and a signifi cantly higher variability of these qualities in the "single" ponds which were situated at a long distance from large pond complexes.

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