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What is Spirulina?

Spirulina is a tiny spiral shaped blue-green algae. It is one of the oldest existing life forms on the planet, estimated to be more than 3 billion years old. It lives naturally in volcanic lakes, or crater lakes throughout Africa, Asia, Central and South America. Indigenous people living around Lake Chad in Africa, and Lake Texcoco in Mexico, have been harvesting Spirulina for thousands of years. Spirulina is a detoxifying, immune boosting, and nutritious food source containing many proteins, essential amino acids, vitamins, and minerals.


Spirulina as a Superfood

  • Best source for proteins, vitamin A, vitamin B12 and iron.
  • Contains 3 times more protein than meat.
  • Contains 15 times more vitamin A than carrots.
  • Contains 50 times more iron than spinach.
  • Very rich in calcium, magnesium, phosphorus, like milk.


Health benefits

  • Perfect food compliment for a healthy diet, particularly for vegetarians.
  • Preventing iron deficiency anemia; good for pregnant women.
  • Strengthening the immune system.
  • Inhibition of mother child transmission of HIV.
  • Cancer prevention through provision of carotenoid.
  • Lowering of the cholesterol level and blood-sugar.
  • Enhancing of natural cleansing and detoxification (cleans pesticide, chemotherapy, radiation).
  • Best food complement for supporting malnutrition programs.





Why we grow Spirulina at Sadhana Forest           

  • The Sadhana family likes Spirulina a lot and the dogs too.
  • It fits perfectly in a healthy vegan diet.
  • The conditions for growing are great: Spirulina has optimum productivity in desert conditions.
  • It is a very sustainable food source.
  • Growing is simple, easy to reproduce and teach, and is low cost.
  • It needs very little water to grow.
  • Our experimental outset can be an important example to be copied, particularly for African partners.
  • It has the highest productivity with the best energy efficiency.
  • Mmm… Fresh Spirulina tastes great!

Where to grow Spirulina

  • A place near your home so the Spirulina can receive care and attention.
  • A warm place. Temperature of the water needs to be between 20°C and 40°C. Spirulina is like us: 37°C is ideal, and it will die at 42°C. If the climate is too cold, you can build a greenhouse.
  • A place with easy access to clean water is preferable. Rain water is good. Hard water is not the best. If using city water let it sit out for 2 days to let the chlorine leave.
  • The pool needs to be in an area with no pollution, as Spirulina absorbs much of its surroundings. Avoid areas with lots of traffic or pesticides.
  • A roof or a tarp is helpful to prevent leaves and rainwater to enter the pool.
  • Spirulina likes sunlight earlier in the day, so a spot that gets sun in the morning is best.
  • Arrange a beautiful area with your love, flowers, etc…

How to grow Spirulina

Preparation of the pond

You need 1 m2 of pond per person. A common size pool for a family is 5 m2. You can use plastic, concrete or natural earth clay mixture to make a Spirulina pond. A natural earth pond structure would be best because it is a sustainable structure and it is also the closest representation of its natural habitat. A circular structure is best as it’s more like a natural lake.

Preparation of the culture solution

We will use our example of a 1000 l, 5 m2 pool. The water should only be 20 cm deep. Any deeper and the sun cannot penetrate as much as it needs to for the Spirulina to grow. For a culture solution for a 5m² pool you need:

• 1000 l water

• 5 kg natural, non-processed salt

• 5 kg sodium bicarbonate

• 50 l ash-water (mix 10 kg ash with 40 l water) or use hot water, let sit in sun for 1-2 days, stir 3 times a day

• 20 l urine

Adding the Spirulina to the pond

Once your pool is prepared, you can start to grow your Spirulina. If you are near an existing Spirulina pond, the easiest way to do this is by obtaining 1 kg of fresh, pressed Spirulina (dry Spirulina will not work). Pressed Spirulina will only stay good for about 3 days, or maybe a week if refrigerated. Slowly mix the pressed Spirulina into 50 l of the culture solution from your pool. Use a strainer to break up clumps. Once the mixture is homogenized mix it into the pool. It’s best to do this in the evening so the Spirulina can settle into its new home overnight.

The second way of growing your Spirulina is by increasing Spirulina culture. Even though it will take longer to grow your pool, you will be able to travel with this bottle of “seeds” for as long as you need (no need to feed it, just fill the bottle 75% full and keep out of direct sunlight).

To increase Spirulina, add 25% culture solution to your seed (if you have 1 l, add 250 ml). Daily increase the volume by 25%. If you start with 1 l of Spirulina water it should take about 1 month to grow to 1000 l. Before increasing always check the concentration is below 3 cm on the spirumeter.

A spirumeter is a tool to measure the concentration of Spirulina in your pool. To make this instrument, attach a horizontal white disc to the bottom of a vertical stick or ruler. From the disc, measure upwards to 3 cm and make a mark on the stick or ruler, and make a second mark at 4 cm. To use, take a cup of the pool water and sink the spirumeter into the cup, closely observing to see when the white disc is no longer visible. If the disc disappears before 3 cm you can harvest, if it is more than 4 cm it is not ready for harvest yet.



From our 1000 l pool we harvest daily about 1 kg unpressed Spirulina. This will vary depending on pool size and conditions.

Steps for Harvesting:

  1. Stir the pool. Skim along the surface with a strainer to remove debris and to mix the pool. Avoid stirring up the ashes and stuff along the bottom.
  2. Check the concentration of Spirulina with the Spirumeter to see if it’s ready for harvesting. If the level is below 3 cm, it’s ready for harvest. If it’s higher than 4 cm, do not harvest.
  3. Set up the harvesting screen.  A 50 micron mesh (screen printing) is used to catch the Spirulina.
  4. Strain the Spirulina. You should process 25% of your pool for harvesting, so if you have a 1000 l pool you’ll process 250 l.
  5. Roll the dough. Collect the Spirulina together in the middle of the mesh. From this step on, try to avoid touching the Spirulina. Roll the ball around to collect the rest of it.
  6. Wash the harvest. Rinse the Spirulina with a solution of 2L water and one tablespoon salt, or with coconut water!
  7. Press the ball. Squeeze out the excess water.
  8. Wash equipment. Wash everything off over the pool with clean water, so you won’t waste water.


Always feed the Spirulina after harvesting. For every 1 l (unpressed) of harvested Spirulina, add 2 l of urine. Also feed 50 ml of iron juice. If you are not harvesting your Spirulina, you do not need to feed it.

  • Iron juice: a handful of rusty nails, 1 l vinegar, Juice of 5 lemons, ½ l starfruit juice (optional)
  • The best urine to feed Spirulina would be from a healthy vegan person who doesn’t smoke, drink, or take any drugs (medicinal or recreational). It’s important to observe your pond because the amount you feed doesn’t stay constant. If the smell of ammonia is strong, add 25% less urine than the daily amount. If the smell is absent and the Spirulina are coagulating or sinking to the bottom, add 25% more urine. For example, if you are feeding 2 l of urine you increase to 2½ l. A hint of ammonia smell is okay.
  • Urine is the best food for Spirulina. It is clean, sterile, plentiful, and it contains many nutrients (8-12% nitrogen which is perfect for Spirulina). If you don’t want to use human urine there are some alternatives you can look into: chemical fertilizers, fermented plants, animal urine, and effluent of biogas.


  • Sometimes small fly ephedra can appear on the pool surface. Skim the surface to remove larvae. Mosquitoes can’t live in a Spirulina pond.
  • If your Spirulina starts to clump up, it needs more nitrogen. Increase urine input by 25%.
  • If there’s excess ammonia it may change color to lighter green, military khaki. If this happens you can add vinegar (5 l for a 1000 l pool) or 1 kg of bicarbonate. You can add 2 cm more water to dilute.
  • A little bit of rain in the pool is okay, the level shouldn’t rise more than 2 cm.  5cm or more – you should add more salt and bicarbonate.
  • A 1 cm raise of water for 1 m2 is 10 liters.
  • If a pool of 1000 l overfills by 5 cm (250 l), you add 1 kg of salt and 1 kg of bicarbonate – 4 g each for 1 liter.
  • Spirulina grows in a very alkaline environment, 10-11 pH, so there isn’t a problem with disease or parasite.
  • It’s good to stir the pool about 6 times daily. If the Spirulina sinks toward the bottom of the pool you need to stir it more.
  • If a brown film suddenly appears on the pool surface, don’t worry, it’s only some of the deposits floating to the surface.
  • It is helpful to keep a harvesting notebook, example below, to keep track of your pool.

        Date            Time        Spriumeter            Harvest                      Feeding              Water            Observations

          4/22/09            7:00            2.8 cm                        1 l nonpressed                   2 l urine                   50 l                     Looks great

                                                                                                                                  50 ml iron juice   

How to eat Spirulina

  • Fresh is the best way to eat Spirulina.
  • Fresh Spirulina should be eaten within 1 day of harvesting.
  • Spirulina is great in juices, salads, fruits, and more. Just remember to never cook it because it loses so many of its nutritious qualities.
  • Dry Spirulina stores well for years.

External links