An example of colonial alga is

Volvox is motile colonial freshwater alga with a definite number of vegetative cells.

Colonial alga is algae in which cells resembling free swimming unicells form groups. They may be large and elaborately interconnected as in Volvox or smaller and relatively simple as in Synura.

Chlorella is an unicellular, non-motile alga. Spirogyra and Ulothrix is a filamentous forms.