Home Grown Spirulina | Lessons From a Failed Experiment

Spirulina is a type of blue-green algae. It’s packed with nutrients and easy to add to smoothies or baked goods. But how difficult is it to grow at home? Join me as I try (and mostly fail) to farm spirulina on my windowsill.

Spirulina is a blue-green algae that naturally occurs in mineral-rich water. It is also a rich source of antioxidants. If you’re wondering what antioxidants are good for - they help neutralise “free radicals”, which occur naturally from our metabolic processes but are increased by factors such as smoking and exposure to pollution. Too many free radicals can damage our bodies and contribute to health problems like asthma, arthritis, and cancer.¹ Spirulina, rich in antioxidants, can help prevent free radicals from getting out of hand, and preliminary research suggests that it could also help alleviate hay fever, help manage cholesterol, and reduce high blood pressure.^2,3,4,5,6 Spirulina can even help us eliminate heavy metals from the body, such as arsenic, lead, and mercury.⁷

This blue-green algae is an iron and protein source and contains many vitamins, minerals, and carotenoids.^8,1 You can add spirulina powder to soups or smoothies or just take it as a tablet supplement. Some people swear by spirulina facemasks, and others sip hot cups of spirulina tea. And it’s not just people that can benefit. Spirulina is emerging as a promising and cost-effective livestock supplement and animal feed that can help improve the health and fertility of animals and the nutritional quality of livestock products.⁹ But, of course, no green powder will cancel out an unhealthy lifestyle. Both people and the animals we raise need a balanced and healthy diet, plenty of movement and fresh air.

As someone with a severe iron deficiency, I need to add more iron to my diet, but I’m also trying to eat as locally and seasonally as possible. As well as fundamentally changing my diet and getting proper treatment, I decided to start sprinkling iron-rich spirulina over my meals. I’ve heard it’s easy to grow and doesn’t take up much space. So, in a flurry of excitement (and possibly active procrastination), I tried growing my spirulina at home using a second-hand fish tank and a grand total of 31 euros. After a month of trying (and mostly failing) to grow spirulina, I’m ready to tell you how it went.

A zero-waste, low-carbon, self-sufficient dream

I’m always looking to make my diet more sustainable. To me, that means eating local and seasonal products from smallholder farmers and avoiding plastic packaging. After 12 years of vegetarianism, it recently also means regenerative meat from my neighbour once or twice a month.

I could arguably get all my iron from red meat. But I need to know exactly how an animal lived and died if I’m going to consider eating it - down to the time it took to get them to the abattoir and the conditions they experienced on the journey. And it also means moderation. Because even if meat and dairy can be produced regeneratively, I don’t think it should be an “everyday” product that we toss into trolleys without a deep appreciation of where that food came from.

But a couple of goat stews a month won’t compensate for my current deficiencies. So, in addition to increasing my consumption of iron-rich veggies like kale, lentils, and broccoli, I want to start eating spirulina daily. And if I could grow most of my iron at home in a second-hand fish tank, a lot of my zero-waste, low-carbon, and self-sufficient boxes would get ticked.

To kick this process off, I need a spirulina starter (dormant spirulina), some nutrients to feed the culture, and a tank for it to grow in. On Etsy, I order a spirulina starter and some premixed nutrients* for 16 euros. Sometimes, people give spirulina starters for free – it’s worth checking your community page.

The seller has mixed reviews. Some people are enchanted. Someone else says the algae solution travelled in a plastic bag “sealed” with a paperclip. The post office was unhappy that they had to repackage a green explosion. Let’s see what happens.

* Author’s note: you could save money by mixing your own spirulina food. I don’t want to buy kilo-sacks of sodium bicarbonate, potassium nitrate, calcium chloride, etc. If this turns out well, I could make the nutrient mix in the future.

A rare and exquisite fish

With the spirulina starter in the post, I look on my region’s second-hand online outlet, Le Bon Coin, for a second-hand aquarium. Nearby fish tanks range from 5 to 500 euros. Luckily, my husband is away visiting friends, so he can’t make sensible suggestions like, “Do we really want an aquarium full of algae in the kitchen?” He didn’t say anything about my last surprise project of a mealworm colony, but I’m aware that I’m pushing my luck.

Fish tank mission achieved. (Photo by the author)

I pick a small aquarium with an air pump for 15 euros. An air pump and a water heater are optional but will make the spirulina grow faster. Like any living thing, spirulina won’t cope well if it’s too cold or too hot. It will die if it reaches temperatures above 39 degrees and won’t grow well if it dips below 15.5 degrees. The air pump can help spirulina growth because agitating the water means more algae get better exposure to sunlight, which they need to photosynthesise.¹⁰ But it is possible to provide this agitation by manually stirring a few times daily. It’s summer here in the Hautes Pyrénées, so I’ll try without a heater for now. That brings my total cost for the set-up to 31 euros.

I collect the aquarium from a nearby village. Matthieu (the man I buy it from) asks me what fish species I will keep. I think I’m witty when I tell him, “spirulina fish.” He thinks my French must be bad, but, a true gentleman, he nods thoughtfully and says, “Perhaps I don’t know this fish.”

Later, my husband gets home. Though surprisingly supportive of the spirulina farming endeavour, he points out that the aquarium is made of plastic. If I’m going to grow a “superfood”, should I be doing that in a warm, plastic environment that hasn’t been designed for food safety?

I told you earlier that spirulina is fantastic at absorbing toxins in your body. Well, it’s also good at absorbing toxic substances wherever it is grown. Metals like lead, mercury, cadmium and arsenic are the most likely to contaminate spirulina, especially when grown in open ponds or open bioreactors.^11,12 To reassure you, a study that tested 25 commercially available spirulina products in different countries found they all had safe levels of heavy metals.¹³ But it’s important to buy spirulina from a reputable company or to grow it yourself in a clean environment and with safe drinking water, or you could end up sprinkling something unwelcome in your morning smoothie.

The spirulina I bought has arrived, and it somewhat ironically stinks like rotten fish. The famous fish tank, meanwhile, has been sent to collect dust in the attic.

I grab a 2-litre glass Kilner jar that I usually store rice in, and it does the job just fine.

The spirulina comes with a helpful letter telling me how not to kill it. It has survived transit by going dormant, so my first task is to help it wake up. I decant it into the glass jar, which I place near a warm (but not too warm) window with some (but not too much) natural light.

By the following day, the spirulina should have recovered from its big journey from Germany to France. It’s time to give it some breakfast. I mix the nutrient powder with water, let it rest for an hour, and then pour it into the Kilner jar.

Finally, I don’t use the plastic air bubbler that came with the fish tank. Instead, I’ll gently mix it daily to make sure as much of the culture as possible gets access to light and can photosynthesise effectively. I’m going down this road because after reading up on food safety, I don’t want to introduce any unwanted bacteria from Matthieu’s late goldfish. Keeping everything clean can help prevent contamination and food-related illness.

After a couple of days, I can see little air bubbles forming. This means the culture is alive and photosynthesising.

More days pass, and I can see a few tiny clumps of spirulina growing, and the little bubbles are still going. So, I add some more nutrient mix.

A week later, the spirulina is definitely growing. But it’s going very slowly. This may be because I’m not using a water heater or air bubbler. I’m disappointed. I thought I would be drowning in spirulina by now – dehydrating it with the herbs from my garden and giving bucketfuls away to my adoring friends. I probably have half a teaspoon’s worth of slimy goo.

One week later, all is not well in Spirulinaville. The spirulina has sunk to the bottom and hasn’t made any progress. I place it closer to the window for warmth and light and add a little more nutrient mix. But then the rain begins.

‘Why is nothing happening?’ (Photo by the author)

After ten days of cool weather and no sunshine, I have grown one measly teaspoon of spirulina. I have wasted a lot of time trying to make it warm enough and adjusting the light exposure, which has not been successful.

I taste a little spirulina to see if this endeavour is worth pouring more energy into. The verdict? No, it’s not worth it. Probably because I butchered this experiment; it is slimy and gritty. I’m sure a wiser person than me could make this work, but it’s time for me to admit defeat and move on with my life.

A teaspoon of Spirulina. (Photo by the author)

Conclusions from a failed experiment

I pop to the shop and buy a packet of spirulina powder for 20 euros – significantly less than I wasted on this failed experiment.

I’m going to leave the spirulina production to the experts. For a parent, it could be a fun experiment to teach kids about photosynthesis or how to keep things alive. You know, before you let them have a pet bunny rabbit. Luckily, my own animals are doing better than this spirulina ever did.