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Spirulina cultivation as part of permaculture  RSS feed

Henri Lentonen
Posts: 70
Location: Finland
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Spirulina is blue-green algae, which in fact is bacteria with the ability of photosynthesis.

Most people only know of the toxic blooms, but educated green masterminds have better knowledge of this tiny algae.

Spirulina is the best algae to grow, for various reasons.

Its cellwall is made from mucopolysaccharides, which allows it direct digestion in humans and animals.

Another popular algae for food, chlorella, has cell wall made of cellulose so it needs special treatment with mechanic pressure or similar, to break down the cellwall so the good nutrients inside the algae can be used by humans.

Otherwise, the algae just comes out as it was: this is a good mechanism of survival, since when predator eats algae, the algae will get nutrients inside the predator and then it is pooped out still alive.

Another good survival way is to produce so fast, that even with predators: the algae will survive, since they just cannot eat it all!

More info about the microbe biology: https://microbewiki.kenyon.edu/index.php/Spirulina


In 24 hours, the spirulina algae can in optimum cultivation setup: triple its biomass.

In perfect conditions, small (10 to 100 m2) pond of spirulina can produce 50-60 grams algae biomass per day per m2 but usually the amount it is about 10 grams per day per m2.

Here is basic info about the cultivation of the algae:



Spirulina has great nutrition and medicine value you can read from that here:



I took only couple hours to make this little text, so maybe add something later if I forgot something important.


Growing spirulina for human consumption should not be the first step, but the best way to grow algae first is to grow it inside in aquarium, just to clean up the air from particulates and dust: to give some extra oxygen also.

The next step should be using the algae as fertilizer to plants, booster in compost and as feed to animals or fish in aquaponics system.

Of course, as spirulina can be used by humans as food: it is great food also to farm animals.

At least cows can use the algae, by directly using the collected biomass, into the drinking water of animals. Feeding fish is more difficult, since you have to make flakes or something similar out of the algae.
As spirulina is grown in optimum pH of 9-10, it will neutralize the acid rain effects in soil. Also, when the algae is alive when used in soils: spirulina can in fact, live in soil and has been found in nature also, from soils.

The high pH is also the one main reason, why spirulina is so fabulous: in high pH, other microbes just simple cannot live. There hasnt been a single case for example salmonella in history, on spirulina cultivation. In other hand, the chlorella has had many.

As long as you maintain the high pH, growing spirulina is very safe. If you grow it as food to animals or humans, you should keep the pH in 10, and rise it to almost 11 in the end of the cycle for at least week, to ensure pathogens have died.

If the pH is too high, spirulina will not die but will go dormant and fall bottom of the pond and it will be hard to collect. One main problem in cultivation, is to collect the algae in simple way.

In soil, spirulina it will produce oxygen to bacteria etc., improving the overall productivity of the crops.

Eventually, the algae will die there, releasing nutrients especially to microbes in soil, but also to plants. You can also dry the algae before adding to soil, but I recommend using live culture and dilute it to water.

(I am not experienced farmer with spirulina, so this is just my reasoning, studies shows also dry spirulina is good fertilizer.)

When the spirulina is applied to the soil, it stimulates growth of plants and increases yield. This has been widely studied and confirmed, but not yet fully understood why it does that.

You can grow spirulina in various ways: from animal wastes, from biowaste (compost tea), even from aquaculture waste waters.

The biggest problem with organic spirulina is, how to give the nutrients from manure/sludge or compost tea since they will make the spirulina water dark and murky, preventing the light from penetrating the liquid.

Using chemical fertilizers for spirulina in the other hand, isnt good for permaculture purposes.

If we use organic sources for nutrients to spirulina, the amount of produced algae biomass: will go down. But in the other hand, we in the permaculture: are not in hurry.

Spirulina can use fresh urine as food and can use also ammonia as nutrient. Too high ammonia in the other hand, will kill the algae or at least inhibit the growth, so urine should be added on everyday basis on small amounts.

Raw animal manure can be used to grow spirulina or you can first use anaerobic digester and use the liquid.

If you intend to use the algae grown this way as food for animals, you should let the algae "starve" about a week when you add no manure: so that the high pH will kill the possible pathogens from manure.

Urine can be added if it is fresh, since it is hygienic.


Spirulina needs basic things: light, carbon and nutrients.

Carbon can be delivered by CO2 from the air, but atmospheric air isn't enough to support the maximum growth of spirulina: even with aeration.

Therefore usually is used natriumbicarbonate (baking soda) to provide the extra carbon for spirulina.

Best way, as I personally think, would be to offer the CO2 from compost to spirulina.

Spirulina can be grown on open ponds on warm climates, but on cold climates it needs additional heat: since the optimum growing temperature is about 35 celsius = 95 F.

For this, I personally think compost is also the best way to provide the optimum temperature for the algae. Spirulina should not be grown under 20 celsius = 68 F.

In lower temperature, too much light can even damage the algae. So you need to shade the culture a little for example in mornings, when the algae is cold in this case.

Shading can be also necessary if the sun will heat up the culture too much - this occurs mostly in closed systems.

Spirulina can use 24 hours light a day and will give maximum cell concentration with this, but its nutritional quality will decrease so you should give it at least 6 hours of rest of darkness in a day if grown indoors.

Maintaining pH high can be tricky - it can also raise up too much by itself as the algae grows.

For raising pH I use lye - wood ash extract, which also sucks up CO2 from air.

Boil about 1 part of wood ash and 5 parts of water about hour, and you should have 12-13 pH lye. If you let it sit a day or two and mix it once in a while, it will suck up CO2 by itself from the ambient air.

If you make any sudden changes in culture, it can affect the algae in negative way: if you raise the pH for example, adjust it slowly upwards.

Adjusting pH down can be done simply by adding water.

You should avoid tapwater, which is chlorinated.

When I started to grow spirulina, I almost killed the whole culture with too much (too intense) artificial light.

Also too much aeration will kill the algae, as the bubbles shear the algae in pieces. As the cellwall is quite soft, it is good for us so we can digest it, but you should always mix the culture gently.

You only need about 5 watts of aeration pump for thousand liter of culture. I had 4 watts in 9 litres so it is miracle, that even some of the algae survived.

Now it is in bigger about 60 liter aquarium, and I have a timer so the aeration is on 4 times a day for half hour: 2 hours in a day together.

Also I have poked a little hole in the hose so that it will not use the maximum power to pump the air to the culture.

Spirulina does not like much UV-light, so if you use artificial lights, take notice of that.

Also the red/yellow spectrum of light is what the algae likes most but white light seems to be best overall: so I don't recommend using only red LEDs for example but using fluorescent tubes or sunlight, and as additional light use the red LEDs.

Spirulina cultures can be bought live in many places, but as I dont know which place is best: you have to search yourself, for example ebay has many sellers.

It would be great to see, that in this forum: people would start to cultivate this algae and share live cultures.

If you buy the culture, I also recommend to buy USB-microscope from ebay to monitor the algae growth. But remember that even they promise 1000x it is just digital zoom - the real magnification of these cheap microscopes is only few hundreds x.

Microscope with real 1000x will cost thousands of euros. So you cannot see the bacteria and other organisms, with ebay "1000x", which may live in culture but you can monitor how the algae grows.

In the beginning of this post, there was a picture of spirulina (and little dot-shaped weed algae, which has been decreasing since I started to rise pH) with my own microscope which was about 20 euros from ebay.


Sources by chapter:


Using spirulina biomass as a fertilizer to plants to stimulate growth and increasing yield:






Using spirulina as animal feed and fish, studies of many different animals including rabbits (you can also give it to dogs and cats):







Using different sources of nutrients for growing spirulina:

- Urine





- Chicken manure




- Cow manure




- Pig manure









If you did get interest in subject, here is something to read more:






Spirulina topic here on permies:

spirulina growing in plants


Zooplankton & phytoplankton (semi-closed ecosystem)

Angelika Maier
Posts: 938
Location: cool climate, Blue Mountains, Australia
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did you try growing it and eating it? And how can I distinguish which is spirulina and which is common yuck? I'd rather feed it to the chooks.
Henri Lentonen
Posts: 70
Location: Finland
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No I havent eated it.

I have grown it just about half year, so I want to study more and use 100% organic fertilizers before I eat it.

Got problems in start, since I didnt read enough: gave too much light, and then too much aeration, which almost killed the whole culture.

Oh, that would be a good idea to add to the text, avoiding too much aeration!
Henri Lentonen
Posts: 70
Location: Finland
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Oh and I forgot to reply on of your questions, sorry about that, I get abstracted often!

Spirulina is easy to distinguish from other algaes couse of its spiral shape.

As far as I know, you will not end up other algae growing up there, which would have that kind of spiral shape.

I am not algae biologist, but I haven't heard that there would even exist a similar algae in that spiral shape - as spirulina.
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