Key to the species of Cladophora
| 1 | Plant coarse, branching pattern conspicuous (not requiring magnification to see) | 2 |
| 1 | Plant soft or fine, branching pattern inconspicuous (requiring magnification to see it) | 3 |
| 2 | Plants with large cells, visible to the unaided eye, branches in fascicles | C. dotyana |
| 2 | Plants with smaller cells, not visible to the naked eye, branches mostly on one side, at times, strongly rebranched and claw-like | C. vagabunda |
| 3 | Plants in short tufts | 4 |
| 3 | Plants bushy or spreading, not tufted | C. sericea |
| 4 | Tufts isolated, pale or dark green; axes and branches frequently with adventitious holdfasts | C. socialis |
| 4 | Tufts sometimes coalescing; yellowish green to olive green, axes and branches without adventitious holdfasts, diameter of cells of second order close to that of primary axial cells | C. laetevirens |