Charophytes possess the capacity to store large amounts of various elements, but until today no studies about known methods of determining CaCO₃ and elements in charophytes have been conducted. Because of the large and varying amounts of CaCO₃, it is difficult to estimate the actual element content in dry mass. Simple comparisons of elements in charophyte plant tissue or between charophytes and higher plants are impossible. The main aim of this study was to investigate through laboratory experiments content of carbonates and elements in charophyte tissue using different methods of decomposition (mineralization). The proposed protocol: determination of calcium carbonate content in plants, determination of elements present in the plant dry mass, and calculation of the element content in the plant dry mass as described.