HomeArticles 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 body 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 a great 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 supplement in tablet form. 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 an 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 decide 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 dreamI’m always looking to make my diet more sustainable. To me, that means eating local and seasonal products 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, as well as 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/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 also 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 it's 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.