The Durowskie Lake situated in Wągrowiec (Poland) is the postglacial lake, used for recreationand sport fishing activities. Its surface is 143.7 ha and the maximum depth is 14.6 m. Few years ago itwas strongly eutrophic with cyanobacterial water blooms. Restoration measures started in 2009 usingthree methods: oxygenation of hypolimnetic waters using wind aerators, phosphorus immobilizationusing iron treatment and biomanipulation measures – stocking the lake with pike fingerlings. The resultsof restoration measures were monitored during International Summer Schools, organized in July, as wellas once every month during growing season, in years 2009-2011. Physico-chemical variables weremeasured and biological analyses were done every year with the same methods, making possible theevaluation of water quality and organism’s composition changes during that time. The results of studiesand evaluation of ecological state due to guidelines of Water Framework Directive indicated progressiveimprovement of water quality and ecological state of Lake Durowskie. The quickest improvementreferred to physico-chemical variables of water quality, but they were highly variable during the seasons.Also phytoplankton changed quickly its composition and abundance, however, macrophytes and macroinvertebrates require longer time for reconstruction of their communities.