What spirulina needs to grow
Four conditions: warm water (25–35 °C), an alkaline pH (9.5–11), a steady supply of sunlight or equivalent artificial light, and a nutrient mix dominated by sodium bicarbonate. The high pH is part of why spirulina is so safe — almost nothing else survives in those waters, so contamination by competitor microalgae is naturally suppressed.
1. Open-pond cultivation
The dominant commercial method worldwide. Shallow rectangular or oval ponds, typically 20–30 cm deep, fitted with a slow-turning paddle wheel that keeps the culture moving and the surface in contact with air. Sunlight does the work; CO₂ is dosed in for growth.
Pros:cheap to build, scales to thousands of square metres, robust to operate. Hawaii’s Cyanotech, Taiwan’s Far East Microalgae, and most of Inner Mongolia run this style.
Cons: exposed to dust, insects, bird droppings; weather-dependent yield; harder to control contamination than enclosed systems. Quality therefore depends heavily on ambient air and water cleanliness — which is part of why Hawaiian production has historically commanded a premium.
2. Photobioreactor (PBR) cultivation
A closed-system approach: clear glass or plastic tubes, panels, or columns through which the spirulina culture circulates. Light penetrates from outside, CO₂ is dosed in, and the entire system is sealed against contamination.
Pros: dramatically tighter control over contamination, temperature, and light; consistent year-round production; better preservation of phycocyanin and other heat-sensitive compounds.
Cons: capital expensive, much smaller scale, and energy-hungry if artificial light is needed. Most European, Japanese, and high-end Indian producers use closed or semi-closed systems for this reason — premium product, premium price.
3. Small-scale and home cultivation
Spirulina is one of the few photosynthetic organisms an enthusiastic home cultivator can reasonably grow. A 50–200 litre glass aquarium with an air pump, a heater, the right nutrient mix, and a window or grow light is enough to sustain a small daily harvest.
Pros: the freshest product possible — fresh paste or wet biomass tastes radically different from anything dried, with the brightest blue-green colour and intact phycocyanin. Fascinating to watch grow.
Cons: meaningful learning curve; quality control is your problem; no third-party testing infrastructure; takes daily attention. The home-grower community is small but devoted, and several of them sell directly from their kitchens — see our forthcoming Growers Series.
Where the world’s spirulina actually comes from
- China (Inner Mongolia): the largest producer by volume. Wide quality range — premium and bulk-market both come from here.
- India: growing fast; outdoor pond dominant; some excellent newer producers competing on quality with Hawaii.
- Hawaii: open-pond, premium positioning, the global benchmark for testing transparency. Cyanotech (Spirulina Pacifica) and Nutrex are the main names.
- Taiwan: long-established industrial producers, mid-range quality, the supply backbone of many private-label brands.
- Europe: France, Spain, Italy, Greece, the Netherlands. Smaller, often closed-system, frequently certified-organic. Premium pricing, low volume, high transparency.
- Africa: traditional dihé harvesting at Lake Chad; emerging cultivation in Senegal and Burkina Faso, often in food-security partnerships.
- Mexico: Sosa Texcoco continued the original Aztec harvest at Lake Texcoco into modern times; some artisanal continuation today.
What the production method tells you about the product
All else equal, closed-system spirulina has higher phycocyanin and lower contamination risk. Open-pond can be excellent if the location is clean and the producer rigorous. Both are genuinely fine sources. The variable that matters most is the producer’s testing rigour, which we cover in detail on the quality & purity page.
Next: trusted brands — the producers and brands the community has come to respect across each of these production geographies.