1. How does it move? It hardly moves or only glides slowly; green or golden-brown cells, threads or boxes

Colour and shape?

Focus up and down: these are often seen edge-on.

1. Golden-brown cell in a glassy box; boat-shaped ones glide slowly to and fro→ Diatoms
2. Green, two mirror halves joined at a waist; crescents, discs or stars→ Desmids
3. Green threads with spiral ribbon chloroplasts→ Spirogyra
4. Thin blue-green threads that sway and glide, no visible chloroplasts→ Cyanobacteria threads
5. A flat green star or plate of cells, or a short row of 2 to 8 cells; never moves→ Still green colonies

Not sure? How to judge size by the field of view · This step looks wrong