How to grow spirulina at home Part I – The light
Spirulina grows naturally in alkaline lakes located in tropical regions. To successfully grow spirulina at home you have to reproduce the same environmental conditions. It’s really not hard if you know what to look for.
Four factors are key to re-create that environment:
- the light,
- the temperature,
- the aeration or agitation of the water and
- the culture medium (or the water in which you’ll have spirulina).
Let’s start with the light:
Spirulina is a photosynthetic bacteria (a blue-green algae is actually a bacteria). This means that just like a plant, spirulina needs the energy from the sun to live. Did you know that sunlight provides the most used source of energy on Earth. Thanks to the sunlight energy derived by the means of the photosynthesis that we have wood, peat, coal, gas and petroleum!
Light is necessary for photosynthetic organisms but different cells have different limits of light tolerance beyond which light can cause damages.
When a spirulina culture is in good conditions, it should be exposed to a maximum of natural sunlight to boost the production; but never over 120,000 lux, which is the equivalent of sun exposure at midday in the tropics during summer.
Grow Spirulina at home – Problems with the light?
If you want to grow spirulina at home, you have to know that when the sunlight is too intense, spirulina can “bleached” within minutes and can be killed. As a spirulina grower, you have to be able to recognized the early signs of sun over exposure and react quickly! Scientists say that spirulina cells are lysed (cell lysis = break down of a cell that compromise its integrity) and when that happen, you should reduce the light intensity immediately to not risk to loose your entire culture.
1. If your culture is yellowish or green-olive it means that the spirulina cells are under photostress (too much light) and the cells are lysing. There is too much light for the chlorophyll to deal with and there is a high risk of cell death. You need to shade the culture now!
To shade your aquarium or pond, bamboo mats or agricultural shades are perfect as they still let some light pass through and won’t stop completely the photosynthesis process.
2. If your culture is yellowish AND foaming, it means that lysis has already occurred and that the cells broken open. The foam you see is the polysaccharides released from the cells into the culture medium. In this case to, you have to shade n
ow! and you also want to increase slightly the agitation. If this doesn’t do the trick, lower the pH with bicarbonate and add nitrogen and potassium (recipe for the culture medium here).
So obviously this is something you want to avoid when you grow spirulina at home and you can preventively shade your culture to make sure you won’t reach the point when the cells have stared to lyse.
When to shade spirulina?
There are 4 circumstances where you should shade the spirulina culture:
1/ if the culture is very warm, over 99ºF or 37ºC, as additional sunlight will increase even more the culture and could eventually kill the culture (if would recommend this thermometer as it also measure the pH – critical for your culture).
2/ if the culture is very cold, below 57ºF or14ºC, here adding a cloth to your culture will help trap the heat, just like in a greenhouse.
3/ if the culture is recovering from any problem and is struggling. There is no need to add stress to the culture…
4/ if you start a culture or if the culture is very diluted (Secchi more than 6, more on the Secchi Disk ). Why? Because of what is called “auto-shading” mechanism. Read this article to know more about this auto-shading mechanism.
So the best place for your spirulina tank when your grow spirulina at home would be next to a window on the South face of your house. Or outside – but only if you life in warm place because the temperature is the second most important parameter to consider when growing spirulina at home (see PART II – The temperature)
How about artificial light for growing spirulina?
Well it’s pretty hard to compete with natural light. Natural light is usually 100 times brighter than artificial light (about 100,00 lux vs. 1,000 Lux). But some spirulina growers have been able to grow spirulina with artificial lamps quite successfully, the productivity is not the same but it’s absolutely doable!
“Green lights” specifically designed for plants are not the best light for spirulina (it will work but you won’t have the optimum grow).
Why? Well, it’s due to the specific set of pigments found in spirulina.
Green plants use a pigment called chlorophyll for the photosynthesis. The chlorophyll absorbs (or uses) red and blue wavelengths (or lights) and will not absorbs the green light; the green will bounce out (and this is why they appear green to us).
Spirulina, the blue-green algae or cyanobacteria, has a unique set of pigments (called phycocyanins and allophycocyanins) in addition to the chlorophyll, and many others which allow to absorb more red and orange wavelengths (lights) than blue and green wavelengths.
Check out this very neat illustration from Spirulina Division showing the different wavelengths spirulina uses to grow:
How to choose the right artificial lights?
If you grow spirulina at home and don’t have the opportunity to place your aquarium close to a window and go for artificial lights these are my recommendations:
- Pick a light that has warmer color (625 – 650 nm). It allows spirulina to absorb a higher fraction of the light and increase the growth rate.
- Put the lights on a timer and set the timer on 16h of light per day. Spirulina do need an rotation of day and night to strive.
Do you grow spirulina at home? What type of light are you using for the moment? Does it work for you? Do you have any challenges with the lighting of you aquarium? Let me know in the comments below!
UPADTE – check out Dennis’ comment about using LEDs for growing spirulina at home. Thanks Dennis!