BLOG#1 -Edible Algae System - (Growing Spirulina in space)

Steps to Growing  Spirulina Algae

This is my 1st blog post in a series of blog post for the Design Challenge 1 Meter of Pi

version 1.1


To grow any Algae there are several product cycles involved in getting a good product:


  • Getting the right Materials
  • Growing
  • Backup Culture
  • Product Harvesting

These steps will be described in detail in this blog

Getting the right Materials together

To grow spirulina, you will need a solution that contains the Spirulina culture along with Nutrients and salts.

To decide the amounts of each nutrient to add to the mix, refer to Appendix 1 at the end of this blog.

Then add some of the mix to water following the measurements list in the table in Appendix 2 at the end of this blog.

Nutrient List

  • Sodium Bicarbonate (Baking Soda)
  • Sea Salt
  • Epsom Salt
  • Potassium Nitrate
  • Ammonium Phosphate
  • Potassium Sulfate
  • Chelated Iron


Spirulina Living Culture

  • A living culture of Spirulina will be needed to be added to the mixture. There are supplies that sell the spirulina culture.
  • The easiest way to get started is to purchase a Kit of all the nutrients, salts and culture in one package  They contain all the nutrients and Spirulina culture needed and included instructions for mixing the solution   
    • There are plenty of Spirulina growing kits available on the Market.
    • Here is one that is available on Amazon, Algae Research Supply Spirulina Farming Kit
    • This includes everting for Growing and Harvesting your Spirulina. It might be a bit to much for a starter kit. There are plenty more to choose from on the internet.


Equipment List

  • Tank
  • Heater
  • Aquarium thermometer
  • Air Pump
  • Air tubing/diffuser w/ check valve
  • Tank Cover
  • Suction Cups
  • Clothespins or clips
  • ¾ plastic tubing
  • Harvest Cloth
  • pH strips



Now your ready to start growing your Spirulina. There are plenty of videos on YouTube that I watched when I was researching for this Blog. I have included  some of them in Appendix 3 for you to check out.


Setting up your Spirulina Growing Tank

For this system, I am using a 20 gallon Tank.

The basic setup of your aquarium should be like this:

  • An air pump connected to tubing that reaches around the bottom perimeter of your tank.
  • A heater connected to a timer.
  • A thermometer on the inside wall of the Tank.
  • A clear tank cover.


Adding the Solution to the Growing Tank

  • Mix up 10 liters of growing medium using the chart (please refer to the charts in Appendix 1 & 2) as reference for how much nutrients to add. Pour your medium into your tank. Before adding the culture make sure to check that your heater can be fully immersed in the water, to go below the water surface it will need to be angled with the top sticking out. This should work fine in a 10 and 15 gallon tank. A larger tank may be too shallow depending on its’ shape. If your tank is too large for the heater to angle in there below the water you may need to do this first step in a different container.
  • Turn your air on to make sure the tubing is placed correctly and doesn’t become detached. There should be bubbles floating up along the walls of the tank.
  • Now you are ready to add your spirulina!
    • It is recommend that you do not add your entire bottle. Pour in about ¾ of the bottle and leave ¼ undisturbed. It is ok for it to be in the bottle without bubbling air, this is your safety spirulina in case anything goes wrong. Just swirl it once a day while you grow the rest in your tank.
  • Once you have poured in your spirulina cover the tank with your tank cover and then cover the entire thing with thin white fabric or take the light source away.
    • You will be adding light later in the process. Let the Spirulina adjust to its new environment.
    • As you can see the spirulina is very thin in the growing medium. This means it is stressed. It needs to be protected from direct sunlight during this time.
    • Each time you double the medium you will cover it during the first days of thinness.
    • As the density grows thicker and thicker you can expose it to more and more direct sunlight.
  • During this first stage of growth the density is thinner than any other time.
    • Monitor the temperature closely, especially during the hottest part of the day.
    • You can check the pH if you want, it should start around 8.5 and slowly rise as the days go by.
    • Be sure to encourage the little guys to grow by talking to them or just spending some time with them each day. This stage is going to take longer than any other stage, maybe a few weeks, so be patient.
  • Use a nonpermanent marker to mark the water level on the side of the tank.
    • During these stages the water evaporates more quickly than usual. As the water level goes down just add more filtered water to bring up the level to where your mark is.
    • You do not need to add nutrients to this added water, you are simply replacing evaporated water.
    • You will do this same process at each stage of the culture growth.
  • Once the culture has reached 4cm or less density it is time to double it.
    • Mix up 10 liters of medium, adjust the heater and thermometer, remark the water level and cover it again with thin fabric.
    • Let it grow until 4cm density.
  • Then you will do the same with 20 liters of water and so on, doubling the medium each time until your tank is full.



Temperature, Water, Co2 and Sun

These are the basic components to growing a successful batch of Spirulina


  • Only use distilled water, not filtered or bottled water.

Temperature of the water

  • between 8C (46.4F) AND  45C (113F)

  • studies have found that the ideal temperature is 35C (95F)

Oxidization in the water (Mixing)

  • Turn On the  AIR Pump

  • 1 minute 3 times a day

Amount of light exposure

  • Studies show to improve the growth rate:
  • a light can be turned ON every hour for 45 minutes and OFF fo r15 minutes
  • From 7am to 10pm

PH levels

  • Check the Ph with a sensor
  • The PH level should be between 9 and 11
  • Adding baking soda can be used to bring up the alkalinity.


  • Check the water level and maintain the same level by adding more distilled water



To grow a successful Algae, there should be a backup batch of the culture mixture in the event that something goes wrong with the present growing batch.

  • All you need to do is keep a bottle of culture (growing medium with spirulina in it) separate from your tank.
    • This can be any clear or slightly opaque plastic or glass bottle or jar that has a fabric cover to let air in but no contaminants.
    • This safety bottle does not need to be aerated or heated.
    • Keep it in the sunlight. It will grow slowly, but that is fine.
    • It is just there in case anything happens to your main tank of spirulina.
    • Swirl this bottle as often as you remember, once a day is best.
    • Change it out if you notice any discoloration, or about every couple of weeks or month.
    • It is good to keep one or two of these as a back up plan in case anything happens to your main tank.  


To tell if the product is ready for harvesting and human consumption you can do a:

Density test

  • Is the Algae growth Thick enough? One way is to observe if a object embedded in the Algae mass is viable from a certain distance from outside the mass.
  • dip a stick with a water bottle cap on the end into the mixture
  • If the cap is not visible at 1.5cm (5 inches) then the spirulina is ready

Harvesting your Spirulina

  • Leave about a 3rd of the mixture unharvested and harvest  2 thirds.
  • Harvest by filtering out the water through a filter.
  • Then add salt and filter water through 2 or 3 times.
  • Store it in the fridge for up to 3 days or put it in ice trays in the freezer


Appendix1 - Mixing Charts

This chart is for making your dry mix of Growing Medium:

IngredientTo make 50L of mixTo make 100L of mix
Sodium Bicarbonate (baking soda)800g1.6kg
Potassium Nitrate (saltpeter)100g200g
Sea Salt50g100g
Ammonium Phosphate5g10g

Extra minerals if you are using distilled,

soft, reverse osmosis or rainwater

Do not add if you are using filtered

tapwater or spring water

Magnesium Sulfate (Epsom Salt)5g10g
Potassium Sulfate25g50g


Appendix 2 - Mixing Your Dry Mix into water

This chart is for mixing your dry mix into water for Growing Medium

Grow Mix7 ½ tablespoons15 tablespoons30 tablespoons


Appendix 3 - Video Reference

There are many video's on YouTube that instruct you on growing Spirulina. Here are a few of my favorites.