In older samples, Oscillatoria limosa forms dark green mats on the mud layer at the bottom or on the side of the container facing the light. There they can be collected easily without many impurities or foreign bodies.

The filaments of Oscillatora limosa often lie parallel together and move against each other (s. figs. 1 and 2). In my population the filaments were between 14–18 µm thick. The individual cells in the filaments are flat disc-shaped, which is typical for the genus Oscillatoria. The filaments show practically no constrictions on the crosswalls. In the cells, however, granules are often accumulated adjacent to the crosswalls (s. fig. 4 a-b). An important feature for identification of the species is the shape of the terminal cells. In Oscillatoria limosa these are broadly rounded (s. figs. 6 a-b and 7 a-b), sometimes with short projections of a membrane sheath (s. fig. 8 a-b). Young cells in the filaments are often strongly vacuolated (s. fig. 6 b). The color of the filaments in my population was consistently blue-green.