An example of colonial algae is
Volvox
Volvox is an example for colonial algae. It is a polyphyletic genus of chlorophyte green algae in the family Volvocaceae. It forms spherical colonies of up to 50,000 cells.
Spirogyra is multicellular algae made up of many cylindrical cells to form a chain called filament.
Chlamydomonas unicellular algae found in stagnant water.
Chlorella is a unicellular Algae found in fresh water.