Arthrospira platensis, aka spirulina, is a helical colony or tricome. Below are some of the features we use to describe the tricome.
Pitch: Similar to wavelength. It is the distance between two peaks in the tricome. The pitch can be between 7-50.
Colony Length: The length of the entire colony. This length is usually 20-300nM. Harvestable spirulina is usually 60-200nM in length.
Diameter: This is the width of the individual cells of the tricome. The diameter is usually 4-7nM.