The two species
Almost all commercial spirulina is one of two closely related species of cyanobacteria, both in the genus Arthrospira:
- Arthrospira platensis — the dominant commercial species worldwide, originally from East Africa and now grown everywhere from Hawaii to Inner Mongolia.
- Arthrospira maxima — historically associated with Lake Texcoco in Mexico, where the Aztecs harvested it for centuries. Less common commercially today but still cultivated.
Nutritionally and visually they are almost indistinguishable. The historical naming — why we still say “spirulina” instead of “arthrospira” — is a taxonomic quirk that the marketing world chose to ignore.
Fresh vs dried
Fresh (paste / wet) spirulina is the product as it comes out of cultivation: a vibrant green-blue paste, soft in flavour, with phycocyanin and water-soluble vitamins fully intact. It must be kept refrigerated or frozen and used within days. Sold mainly by small farms and home-growers near urban markets.
Dried spirulina is what almost everyone buys: the same biomass, dried and shelf-stable for 18–24 months. Some bioactive compounds (notably phycocyanin) are partially degraded by drying, but the protein, iron, and most B-vitamins survive well.
Powder, tablets, and flakes
All three start as the same dried biomass. The differences are convenience, density, and a small amount of processing:
- Powder — the raw form, cheapest per gram, most flexible for cooking and smoothies, and the most flavour-forward. Choose this for kitchen use.
- Tablets— powder compressed with a small amount of binder (usually cellulose). Convenient, swallowable, but adds 5–10% non-spirulina mass per tablet. Choose this if you don’t want to taste it.
- Flakes — powder run through a low-pressure extruder. A halfway form; easier to sprinkle than powder, less concentrated than tablets. Has a small but loyal following for salads and toast.
- Capsules — same idea as tablets, in a vegetable cellulose shell. No meaningful nutritional difference; pick whichever you swallow more comfortably.
“Blue spirulina” — the special case
Sold as a vivid blue powder for smoothie bowls and cocktails, “blue spirulina” is not actually spirulina — it’s extracted phycocyanin, the blue pigment isolated from the rest of the biomass. It carries phycocyanin’s antioxidant properties but none of the protein, iron, or B-vitamins of whole spirulina.
It’s a perfectly fine food colouring with a real bioactive payload — but it is not interchangeable with whole spirulina, and is usually 10–30× more expensive per gram of phycocyanin delivered. Buy it for the colour, not for nutrition.
The honest summary
For 95% of users, the choice is between powder and tablets of well-grown Arthrospira platensis, dried gently. The species, the form, and the colour-extracts are nice to know about, but they’re second-order decisions compared to source quality and testing.