SUMMARYThe present results are the effect of bioprospecting of an appropriate medium, which could optimize the quality and quantity of the microalga Pseudopiediastrum boryanum var. longicorne Reinsch biomass cultured in a laboratory photobioreactor for biosorption purposes. Four liquid media commonly used for cultivation of green algae of the genus Pediastrum were compared, including Knop's, Waris‐H, Chu's and L‐S2T2 media, which differed with respect to the composition and concentration of nutrients. A number of the parameters characterizing biomass growth, namely dry weight, optical density, chlorophyll a concentration, as well as morphological parameters characterizing the condition of the alga and its surface area indicating the potential sorption capacity (population structure, cell number, coenobium size and marginal cell size), showed a significant impact of culture medium on the growth of the microalga. The most productive culture was found in the L‐S2T2 medium containing organic substances in the form of peat and soil extracts, which could be crucial for biomass production and the area of potential sorption capacity.