Five-Ingredient Growth Medium for Spirulina Algae

Mix the following into a liter of water:

• 16g Baking soda (sodium bicarbonate)
• 2g Saltpeter (potassium nitrate)
• 1g Sea salt
• 0.1g DAP (diammonium phosphate)
• 0.1mL¹ Liquid chelated iron sulfate with 3.5% chelated iron content

Took a while to find an algae growth medium that didn’t either list 18 chemical compounds or contain ingredients like Single Super Phosphate that are difficult to find in the United States. Finally ran across this one mentioned off-hand by Dr. Cath of Spirulina Academy, buried deep in a comment thread under one of her articles².

Each ingredient is easily found on Amazon, and often in natural food, bulk food, or co-op / farm supply stores. Make sure you get food grade if you’re planning to eat the Spirulina. If this is just an experiment or hobby, buy the small sizes of everything rather than optimizing for $/g since the amounts used per liter are so minimal (except for baking soda).

So how well does it work? So far so good! My 20L of algae have thrived in it over the past year. Haven’t run any rigorous controlled trials, but in a side-by-side run with 2L each of the Five-Ingredient Growth Medium and Zarrouk’s Growth Medium the culture’s population density appeared to increase at the same rate.

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