Charophytes are a key group of submerged macrophytes in temperate hardwater lakes. Their decline started more than 100 years ago, but this process is continuing in many European lakes despite an overall reduced nutrient loading. Consequently, many species are strongly endangered or even threatened with extinction. We used data of 92 NE German lakes covering the last two to four decades to investigate long-term trends in their charophyte vegetation. In addition, we investigated the potential impact of periphyton shading and fish on charophyte abundance in oligo-mesotrophic hardwater lakes. To measure the influence of periphyton, we exposed artificial substrates in summer to 11 lakes along a gradient of charophyte abundances. We also performed a large-scale enclosure experiment stocking roach (Rutilus rutilus) and bream (Abramis brama) at a biomass of 0, 50, 100 and 250 kg/ha to large enclosures (35 x 60 m each) in a lake containing charophytes. Periphyton was measured on artificial substrates and in underwater videos estimating periphyton abundance. In the lake survey, charophyte abundance was significantly predicted by the biomasses of periphyton and benthivorous bream. The enclosure experiment revealed significantly positive relationships between fish biomass and physical disturbance as well as physical disturbance and periphyton abundance. Based on these results we will discuss options for charophyte restoration in hardwater lakes.