It is a common component of the phytoplankton of freshwater habitats, particularly eutrophic and alkaline waters.

The name was first coined in 1895 by Robert Chodat for the species Tetrastrum heteracanthum, which was previously placed in the now-obsolete genus Staurogenia.

Cells are tightly joined in a flat plane, with or without a small space in the middle.

Four autospores are formed, organized into the shape of the colony; these are released through a tear in the mother cell wall.

[3][4] Species of Tetrastrum are identified based on the size and shape of the cells, placement and length of the spines, and presence or absence of pyrenoids.