We modeled ecological optima of the four commonest Philonotis species in three regions of Europe, using measurements of pH, water conductivity, altitude and vegetation gradients. We did not observe obvious differences in ecological optima among three climatically and geographically different regions. Philonotis calcarea was well separated from other species along the water pH and conductivity gradient and occupied the most mineral-rich and alkaline springs in all cases. Philonotis seriata was at the other end of the mineral-richness gradient. The morphologically similar species, P. fontana and P. caespitosa, had very little differentiated niches with respect to water pH and conductivity, which differed slightly among regions. We concluded that species with clearly differentiated niches like P. seriata, P. fontana and P. calcarea are accurate indicators of the chemical parameters of spring waters.