Oribatid mites are mainly terrestrial animals, but some are aquatic, including all species of the genus Hydrozetes (Hydrozetidae). They have often been recorded in abundance on the water's surface, while their presence in the benthic zone is poorly documented. A litterbag experiment was carried out in Coutos Lake, a shallow temporary lake in Southeast Brazil, in order to study the ecology and biology of Hydrozetes paulista. This mite species greatly dominated the benthic invertebrate community (82%), and at the end of the experiment it reached a density (652 individuals per 1 g of dry substrate) higher than that ever previously reported before for any Hydrozetes species. This density was correlated with some water parameters, stronger with conductivity, and less with temperature. The adults dominated in the stage structure (constituting over 80% of sample population), but the participation of the juveniles increased with the time. Larvae were first noticed on 25^th day of experiment and after that were present for the rest of the season. During the course of this experiment, mite fecundity and body size decreased. This species is known as bisexual, but we observed only females in the 5354 adults we collected.