All About Spirulina Growing Basics

Spirulina Fundamentals - What You Should Know Before Growing Spirulina

Light - The Right Light to Grow Spirulina

When spirulina is good and strong the rule of thumb with light is the more the better. Sunlight is best and will provide the most growth for your spirulina. The more surface area of your growing medium that is exposed to sunlight, the better. If you have a lot of sunlight you need to be aware of how much heat is added to your tank during the sunniest times of day.

You may be surprised at how the temperature will rise when you grow Spirulina in the sun. Be sure to monitor this as you are learning to grow your spirulina and as the seasons change. Your spirulina will die at a temp of 102 degrees Fahrenheit (38 degrees Celsius), which is pretty close to the temps they like to grow at. So be careful! Notice above that we said that the more sunlight the better is for when the spirulina are established and strong. When you are first growing your spirulina too much sunshine can hurt them.

When you are in the process of doubling the amount of your growing medium you want to shade the spirulina. Do this by placing a sheer fabric over your tank. See through white fabric is best, but if you don't have that experiment with what you do have. The rule of thumb is that if you can see through your medium then it is a good idea to shade it. Once the green spirulina has grown thick enough that you can't see through the tank then take off the fabric. If you are interested in growing spirulina with artificial light it might be a good idea to do some research on the internet. We have not grown spirulina this way before, but as we understand it normal plant grow lights do not appeal to spirulina because they are in the blue­green spectrum. Spirulina prefers light which is in the orange­red spectrum for growth. Some flourescent lights provide this and you can also find specialty led lights. We would love to hear about anything that works (or doesn't work) for you, please let us know by email or on the forum!

We recommend starting with a Spirulina growing kit because it will be much easier.

Temperature - The Right Temperature to Grow Spirulina

Spirulina like to have a fluctuating temperature cycle (And if you bought a spirulina growing kit, you almost certainly got an aquarium heater). They like it warm and sunny during the day and cool at night. The optimal temps during the day are 34 degrees Celsius. Anything around 37 degrees and over and they will start to die. This is the most common cause for culture loss. It won't happen all at once, so don't panic if the temp climbs too high, but do something to change the environment.

Spirulina like to cool down quite a bit, but they don't like to go below 20 degrees. This generally won't happen if you are operating your tank normally

The way to keep your spirulina happy is to have your heater connected to a timer. Have your timer set to turn on two hours before sunrise and turn off around sunset. Be aware of the change of seasons and adjust accordingly. If it is the middle of summer you may want to have your heater turn off again during the sunniest part of the day so that the temp doesn't rise too high.

Water - The Right Water to Grow Spirulina

It is very important to use the right water! If you add unfiltered tap water to your spirulina it could kill them due to chlorine content! The easiest and often best source of water is FILTERED tapwater.

You can filter tapwater through a carbon filter or a ceramic filter and this will clean out the chlorine content. Brita, Pur and Berkey filters work well for this. If you are using a filter that is connected to the tap make sure it has been changed and updated according to it's instructions. An old, clogged or overused filter may not clean out all of the chlorine. If you have tapwater but choose not to filter it you can also get a dechlorination kit at your local pet store.

Treat Springwater just like tapwater. It shouldn't be chlorinated when you get it, but it is a good idea to filter it just to be safe. If you want to use distilled water, rainwater, “soft” water or water that has been filtered using reverse­osmosis then you will need to add extra minerals. All of these waters lack the mineral content necessary for happy spirulina.

Refer to the mixing charts for the amounts and types of extra minerals needed. DO NOT USE “alkalized” water, such as from a Kangen filter, the pH is totally wrong for spirulina.


It is normal for the algae to coagulate in clumps as they grow. This is one of the reasons for keeping the medium moving along the edges of the tank, to inhibit clump growth. You will find that as you maintain and harvest your algae that clumps will detach and float at the top of the water. It is okay to filter and consume clumps that are very dark blue green. DO NOT EAT ANY CLUMPS OR ALGAE WHICH ARE CLEAR, WHITE OR YELLOWISH. These clumps are a normal part of the spirulina process. Just remove them from the medium using a small strainer or spoon and dispose of them.

Remember to add 1 tsp of feeding mix and a small squeeze of iron to every 2 tbs of clumps removed. As you get to know your spirulina you will understand what is a normal amount of clumping for you tank. If your tank is suddenly producing too many clumps something is wrong. Before you become alarmed think if you have recently poured an extra heavy stream of water into your tank which simply loosened a bunch of clumps which may have been on the floor or elsewhere.

If you have been operating as normal then either your tank is too hot, the mineral content is off, or it has become contaminated. Monitor your temps, check your pH often and perhaps add some extra nutrients or iron, or less if you may have added too much. If the over­abundance of clumping continues renew your growing medium.

If you are concerned about contamination (there is a strange smell or more discoloration or other colors) check your culture under a microscope. If in doubt, throw it out.