Species guide
Arthrospira (Spirulina)
Arthrospira is where Algaephyte started. It is a filamentous cyanobacterium — photosynthetic like an alga, classified as a bacterium — cultivated for millennia around alkaline lakes and now grown in photobioreactors and open ponds worldwide. Every culture concept on this site, from twins to fail-closed dosing, was prototyped on it.
- What it is
- A filamentous, spiral-shaped cyanobacterium (a photosynthetic bacterium, not a true alga) sold worldwide as the food 'Spirulina'.
- Taxonomic group
- Cyanobacteria; the cultivated species is usually Arthrospira platensis.
- Typical appearance
- Blue-green helical filaments (trichomes), recognisable as coils even under modest magnification.
- Typical size
- Filaments commonly a few hundred micrometres long, several micrometres wide.
- Culture characteristics
- Grown in warm, highly alkaline (pH ~10), carbonate-rich water. That extreme chemistry excludes most contaminants — a rare biosecurity gift. Strong light and agitation suit it.
- Major applications
- Human food and supplements, phycocyanin (blue pigment) production, animal feed enrichment, research into alkaliphilic photobioreactors.
- Typical users
- Food and supplement producers, pigment processors, home and commercial growers, photobioreactor developers — including us: Algaephyte v1 was built on Arthrospira.
Why aquaculture values it
Arthrospira is the one microorganism most people have already eaten. In aquaculture it appears mainly in ornamental fish feeds, broodstock diets and enrichment products rather than as a marine larval feed — its filaments are far too large for animals like bivalve veligers. Its cultivation story matters to feed culturists for a different reason: it shows how extreme culture chemistry can substitute for sterile technique.
Nutrition and important compounds
Dried Arthrospira is famously protein-rich (roughly 60–70% of dry weight) and is the commercial source of phycocyanin, the blue phycobiliprotein used as a natural colourant. It also carries gamma-linolenic acid and a range of carotenoids. Exact composition varies with strain and conditions — published percentages are ranges.
A note on culture parameters
Culture parameters vary substantially between strains and systems. The alkaline approach is well established, but exact temperature, salinity, medium recipe and harvest timing differ between producers — including between our own Algaephyte columns and anyone else's. See our field notes in the insights library for how we actually run it.
Frequently asked questions
Is Spirulina a plant?
No. Arthrospira is a cyanobacterium — a photosynthetic bacterium. It shares oxygenic photosynthesis with algae and plants, which is why it behaves like an alga in culture, but taxonomically it is a bacterium.
Why is Spirulina culture 'self-protecting'?
Its preferred medium is so alkaline and carbonate-rich that most bacteria, fungi and grazers cannot live in it. Contamination control is built into the chemistry, which is unusual among cultivated microorganisms.
Can I feed Spirulina to marine larvae?
Generally no — the filaments are too large for first-feeding guts. Marine live feeds use small microalgae such as Isochrysis, Pavlova and Chaetoceros. See our bivalve rations article for stage-specific detail.