Abstract The cyanobacteria are an extremely varied group of gram-negative bacteria with different chemical and physical features. Phycocyanin is a pigment found in every member of this group. It helps with the process of converting atmospheric nitrogen into organic nitrogen, specifically ammonia (NH3). Two different cyanobacteria species were studied for their ability to fix organic nitrogen in order to achieve the goals of this research. The strain of Crinalium magnium (Oscillatonales Oscillatonales) that does not cause heterocytosis and the strain of Fischerella muscicola SAG 1427-1 that does produce heterocytosis are the two strains that in question. In the course of the investigation, it was discovered that both categories of organisms have the ability to fix nitrogen from organic matter. In terms of the fixation of organic nitrogen, the findings revealed that the strain F. muscicola had a considerable advantage (563 mg/l) when compared to the strain C. magnium, which had a value of 395 mg/l when cultivated in the medium Chu 10, which is devoid of nitrogen. The findings also demonstrated that the F. muscicola strain significantly outperformed the C. magnium strain. When compared to the carbohydrates content (480 mg/L) and the protein content (465 mg/l) of the strain C. magnium, it was observed that the value of the carbohydrates content (540 mg/l) and the protein content (505 mg/l) for the strain F. muscicola increased after 15 days in the medium Chu 10, which is nitrogen-free. This was the case when comparing the two strains. In contrast to the strain of C. magnium, this was demonstrated to be the case.