Volcanic areas with highly acidic solfatara soils and temperatures of up to 56 °C are inhabited by the red algal genus Galdieria. We examined three highly acidic but non-volcanic habitats in the western part of the Czech Republic for the occurrence of this red alga. In soil samples from the National Nature Reserve of Soos we found, together with Euglena mutabilis, Pseudococcomyxa simplex and species of Chlorella, a new strain of Galdieria. In contrast to all other Galdieria strains described so far, the strain from Soos exhibited a low temperature optimum for growth of about 30 °C. Other properties, such as the substrate spectrum for heterotrophic growth, ultrastructure, fatty acid composition, thermostability of enzymes and the nitrogen source, showed no obvious differences from other strains of Galdieria. Within a phylogenetic tree based on 18S rRNA sequence data, the strain from Soos occupied a position at the base of the ‘Galdieria’-branch. Our findings indicate that the genus Galdieria is not restricted to volcanic and mining areas and that strains of Galdieria are able to compete successfully with green algae in habitats like Soos.