I'm pretty impressed with Spirulina.
Spirulina is an algae (actually cyanobacteria) with an amazing nutrient profile, which can be farmed with relatively minimal effort once you've climbed the learning curve.
Although farming it under its own ideal conditions does require energy investment to keep the culture at ideal temperature, and loaded up with plenty of light, Spirulina will grow -- just not as efficiently -- under whatever natural Sunlight conditions it receives, and can exist within a reasonable temperature range. It will die if it gets too cold (< ~45'F) or too hot (> ~108'F), but beyond that, growth suffers. See chart:
Obtaining a Culture
There are a handful of reputable sources. I have sourced spirulina platensis from, and can personally recommend:
- Algae Research Supply -- available through Amazon
- Dr. Aaron Baum (former NASA)'s AlgaeLab.org; his book is authoritative and can dispel much confusion you might have after noticing the CONFLICTING information on the web
Building a Medium: Recipe
IAF video: https://www.youtube.com/watch?v=ff8SzDBq3fY
For each 10-gallons of medium you are building out:
- Baking Soda (Sodium Bicarbonate): 600g — $15 for 5lbs, or Arm & Hammer works fine!
- Saltpeter (Potassium Nitrate) 75g or 2 1/2 Tblspn — $3 for 500g plus shipping, (I thought that was too good to be true but it’s the same as what ships from their store for 2x price, go figure)
- Sea Salt (NaCl + trace minerals) 38g or 2 1/4 Tblspn — health food store
- DAP (Ammonium Phosphate, or Diammonium Phosphate) 3.8g — 2lbs for $10
- Now: Iron Supplement: Ferrous Sulphate — $9 for 16oz
- this will be mixed with a chelating agent like lemon juice or green tea before introducing to medium
- I switched from the EDDHA iron chelation to something food grade: Iron Sulfate supplements, to be combined before introducing into the medium with again a food grade chelating agent (lemon juice).
Once your culture has grown into its medium and the pH has stabilized above 10, you are ready to harvest.
Harvesting requires a 50-micron screen, which will catch the individual algae cells, allowing the nutrient solution through to be replaced into the culture to grow more!
Feeding your Culture
As you harvest, you will need to feed your culture to replace the nutrients removed by virtue of harvesting algae.
The nutrient mix is different than the medium recipe. These RATIOS will work to make any amount of nutrient mix; in this case, the amounts reflect a target of 1.5 kg:
- Saltpeter (Potassium Nitrate): 1400g
- DAP (Ammonium Phosphate): 50g
- Potassium Sulfate: 30g
- Epsom Salt (Magnesium Sulfate): 20g
Mix well. The mix will keep for some time, as long as it stays dry.
If harvesting 2g of fresh spirulina, add 1g of nutrient mix. And, every 2g of nutrient mix or so, add a squirt of the iron we chelated above.