Spirulina - Setting Up a Home Cultivator

in food •  24 days ago

Now that I’m back home in Mexico City again, it’s time to re-assemble my urban homestead, piece by piece. Today I want to show how to set up a spirulina cultivator. Unlike my previous one, which was a huge system of 300 liters (79 gallons) that would only fit on the roof, I’d like to keep this one small. Two carboys of 15 liters (4 gallons) each should be sufficient to grow enough spirulina for our own consumption. Also, since this system can be easily assembled in our apartment, it will be possible to control the water temperature, and hence grow (hopefully) more than in the big one. We’ll find out. So let’s see, what is needed in order to grow spirulina in your home:

The Receptacle

I used two 20 liter (5 gallon) carboys. These plastic bottles are super common here in Mexico, where the tap-water is generally not considered clean enough to drink. More on that in another post…

I cut off the top of the carboys so I could have easy access to the inside. This will be useful later on when it’s time to harvest, and of course it’s easier to clean them too this way. With the top gone I don’t fill them up all the way, only at ¾ capacity, or 15 liters (4 gallons) is plenty. But before I fill the second tank, I want to let the spirulina grow in the first one.

The Right Kind of Water

The most important thing for this nutritious blue-green alga is its growing medium, that is water. But not just any kind of water! It needs to be slightly saline, and very alkaline. To achieve this, we take regular tap water, and add the right amount of salt and baking-soda: For every 10 liters (2.6 gallons) of water you need 100 grams (3.5 oz) of baking soda, and 50 grams (1.8 oz) of table salt. (Sure, I converted it to imperial units, though it doesn’t give us such nice numbers, so easy to remember.)

If you live close to the ocean, you can also mix sea water with fresh water at a ratio of one saltwater to two freshwater. You’ll still need the baking soda to raise the pH, of course. The ideal pH is 10 or above, but I’ve put spirulina in water with pH of 9, and it still worked. Once it starts growing, it’ll help raise the pH too. Since I couldn’t find any pH test strips, I’ll just trust that the baking soda has done a good job, and the water is at the right pH.

Adding the Spirulina

Once the salt and baking soda is completely dissolved you can add the live spirulina. How do you know it’s live? Simple: it looks like green water, since it’s dissolved in its growing medium. Once harvested, that is taken out of the water, it starts dying, and quickly turns black (with a horrible smell and probably an even worse taste). To keep this from happening, the alga is dried, frozen, or dry-frozen. In either case, it stops being useful for starting a cultivation.

Once in the water, the spirulina may as well be given its first feeding. It will grow anyway, but like all of us, it performs best when all its needs are met. To feed it, you need urea and extra iron. I’m sure they sell these ingredients produced industrially from a laboratory, but you can go straight to the source: your pee! As for the iron, it’s not too hard to make the iron insume the spirulina loves.

A feeding consists of 100 ml (3.4 fl oz) urine for vegetarians, or 85 ml (2.9 fl oz) for carnivores, and one ml (0.03 fl oz) of iron insume. For the former part I recommend a pee-bottle, marked at the proper volume, for the latter part a syringe.

Preparing the Iron Insume

The recipe is simple: **Take 100 grams (3.5 oz) of rusty nails, put it in a liter (a quart) of white vinegar, and add the juice of four limes.** Now all you need to do is wait for two weeks, strain the solid pieces, and the liquid is going to last you for the next few years…! Oh yes, since it takes two weeks to prepare, it’s most recommendable to do this ahead of time, before feeding the spirulina.

Movement and Temperature

Now that everything is added, you don’t need to do much more. The spirulina is going to grow if it feels happy. As it grows, the alga tends to stick together, forming pieces, and floating to the top of the water. As more of it rises to the surface, the first pieces get pushed out of their growing medium and die. To prevent this, the water needs to be kept moving constantly. For this I use a simple aquarium pump. The one I have can be easily hooked up to keep two carboys bubbling. I just had to weigh down the hose with a rock so it stays at the bottom.

The other important part is the temperature. Spirulina grows best if the water is between 20°C and 35°C (68-95°F). If it’s colder than that, nothing will happen, the spirulina is just going to sit there without growing, but alive. If the temperature gets higher than the optimal growing range it will get cooked! This is why I consider a thermometer way more important than pH test-strips. This thermometer comes combined with a hydrometer, helping you check the salinity (1.01 is what you need). It's neat, but even less necessary than the pH test strips.

This is the tricky part, by the way! I have a simple water heating device, which I tried before adding the culture. It heats up the water quite quickly, which I’m not too fond of. However, I’m gonna have to give it a 5-10 minute heating each day, just to get the water to growing temperature. In my big cultivator on the roof I didn’t even expect a harvest until March, when the night-time temps wouldn’t drop too far, and the water tank would stay above 20°C.

All You Need Summed Up

Here is a list of all the things you need to start your own spirulina cultivation:
a container, a pump, a heater, a syringe, a thermometer, and a pee-bottle. pH test strips are useful, though they’re not in the picture. Other than that you need some salt, some baking soda, rusty nails, vinegar, limes, your urine, and of course some live culture, ideally gifted by another spirulina enthusiast.

So, that’s pretty much it. Doesn’t seem to hard, does it? I’ll write another spirulina post on how to harvest the spirulina, once the time comes for in a couple of weeks, and of course how to know that it is ready to be harvested.

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I didn't know you can grow algae at home like this. The process sounds quite difficult and long but the result must be very rewarding. I would love to have my very own grown spirulina at home instead of the powder that I have to buy every time. How did you get to such scientific growing of whatever you need to grow? To me it sounds like lots of chemistry which I was not very good at :)

Thank you for sharing!


Well, it's really not any more complicated than maintaining a fish tank, and once it's up and running you are flooded in spirulina. With the big tank for certain, but even with this little one there should be a continuous supply of it. But give me a couple of weeks, and I'll write more about it. And yes, the reward is delicious creamy spirulina that tastes a thousand times better than the dried stuff (yuck!).

How did I get into it? It all started with the question: what can I grow in an urban setting? After mushrooms, kombcha and other probiotic drinks, spirulna was the next logical option. The rest was simply following the info trail, meeting like minded people, and then trying it for myself.


I can't even imagine how the 'fresh' thing taste like! It's simply not available in Switzerland as the sea is far far far away :) I'll be looking forward to reading more about this topic..

Recently, I've been looking into fermentation but didn't get the guts yet to start. It all somehow looks so scary. I travel a lot and I'm afraid that my products would die by the time that I would get home (if they would be still in progress of course)

But I think it would help me to meet like minded people. So it's a good point from you. I will see if there are any communities like this around here..


oh, you don't need to live by the sea to grow spirulina! I live in Mexico City, which is even further from the sea than Switzerland. All you need is table salt, and not even a lot: five grams per liter.
And you're right, cultures are just like pets. Spirulina is actually a lot like a cat: it fends pretty much for itself, so it doesn't need you as much as a dog, still you can't completely leave it alone for an extended time.


That is good to know! I will look at my schedule and hopefully will find at least a month this year that I will be at home so that I can try something :)

Have a great weekend!

That is super impressive..wow. I think my experiments fail as I lack scientific rigour.

Where do you get the spirulina from in the first place?

Calling @alchemage .. I think he'd appreciate this one.

Resteemed on Natural Medicine.

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Well yes, that's the tricky part! I got mine from my buddy Gerardo, who's also a keen spirulina grower. Otherwise there's this company SpirulinaViva who can sell you cultures and ship it to anywhere in Mexico. But there are countries, such as Canada, where I have not been able to locate anyone selling it in the entire six months while I was there last year. In the States it's easy, you can order it from the huge retailer that used to be an on-line bookstore.

Thanx for the re-steem, by the way! :-)

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I use spirulina in my diet and pay a fortune for it. Where do you get it in liquid? The kind I get is usually from Hawaii and is black. I wonder if that is ok now? So many questions! I hope you will keep posting more about this.


Black??? Wow! My spirulina has turned black at times, but it always came with a horrible, rotten smell, that made me not even want to try it. I'm no fan of dry spirulina either, as I find it much worse tasting than the fresh stuff, but that blackness was even beyond that. This happened when I let it dry out, when it was pushed out of the water by more spirulina growing under it, or once we tried to put it in a quesadilla, and almost immediately it turned black when exposed to heat. One time I also tried to deliver it, and on the 1 hour+ bus ride it melted (I usually store it in the freezer) and started dying. By the time I arrived it was but an awful black goo. So in my experience black means not good. Deep green almost blue is the best, light green on the way to yellow means trouble but still okay to eat, brown is on the way out, and black is gonner. But there may be different varieties, I don't know.

I got the cultures from a friend. As I replied to another comment, it depends on where you are. In Canada I could not find anyone to sell me any, as hard as I tried. In the US you can order it on-line without problems (though for a pretty penny, which in my opinion is way worth it. If you do it right, it may be the last spirulina you'll ever need to pay for).


Maybe. I will try to find it. I am in Malaysia, so I might be on quite a quest! The powdered type I have had was so dark, and I now think it was dead as you say. I just use in is drinks and have never tried to heat it.


Who knows... you may be surprised in Malaysia. As I said, in Canada it was impossible to find, while in Mexico all you need to do is do a quick web-search, and they ship it to your place for not even a lot of money. Plus there are other people growing it. Since weather in Malaysia tends to be nice and hot, I could imagine it being a popular thing to grow. (As I said, keeping the water temperature above 20°C is the most tedious part of the whole thing.) Good luck finding it!


Thank you! I am going to be keeping my eyes open. They sell the jarred spirulina in the pharmacies here, so they know it is for health :)

That is a very interesting process! Great details and instructions!


Thank you! Please stay tuned for further details on checking the concentration, harvesting, and of course using this great food.

Fascinating to learn about growing this wonderful power food at home! Do you think the beta-carotene makes it harder to get a sun burn?


Hahaha, could be! Maybe that's how I managed to get away without a sunburn...? Though at the time I didn't spend so much time in the sun either...

Awesome post, growing spirulina (and chlorella) has long been an interest of mine.

But as a biology major, and having read a whole lot on growing spirulina in the past several years, without tops on your containers, how do you prevent it from being contaminated by other, potentially toxic, algae spores?

The only people I know who grew spirulina in the past checked it regularly for contamination, microscope and all, and so please understand, I'm not snarking, but I am concerned.

Hope you can set my mind at ease.

That said, if your method really works, it is exponentially easier than I've been led to believe. Thanks again.


Well, I'm not sure if this is going to set your mind at ease... but what I've been told, is that in such a highly alkaline environment other algae would simply not thrive. My last cultivator was also anything but hermetically sealed, as you can see in the video. It's basically a tent, a series of tarps, but the stuff grew in it like crazy, and the only contaminant I had to pick out occasionally were flying insects that had fallen into the water.


Cool, great to know.

I've been mostly talking to, and reading, researchers and scientists used to formal clean room set ups, so their mindset isn't exactly on DIY procedures.

Love Spirulina, and looking forward to getting this going!!!

For those considering this, you can buy cultures on eBay and Amazon, just check out the reputations of the seller first. Some Scientific supply companies also sell to the public.

Also, for anyone raising tilapia or other fish in an aquaponic system, consider raising your fry in a "green" aquarium full of beneficial algae.

When I got my first certificate in aquaponics, the guy giving the class told us that they had taken a single hatching of fry and separated them into two groups.

The first batch of fry was raised in a "green" aquarium, full of algae (as I recall they were using chlorella), and given no supplemental feed. The second batch were raised in a typical "clean" aquarium and fed crushed pellets.

By the time the fry were ready to be moved into the main system, the fry raised in the green aquarium were twice as long, and between three and four times the weight or more, as those raised in the clean tank and fed pelleted food.

Less work and far better results! Works for me.

And spirulina, also being beneficial and high in protein, not to mention far easier to digest than chlorella, should work at least as well.

Good luck!


Wow! Thanks for such detailed information.


You're welcome!
Obviously I've been studying this stuff for a while. ;-)

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I had never heard of spirulina before. Thanks for the info.
Once you harvest this spirulina what do you do with it?


What I do with it? Eat it of course! If not selling it at the market. To store it I put in in the freezer. But in a few weeks when it's ready I'll make sure to post about it, showing exactly how to use it.