Home Forums Growing Spirulina Yellow sediments and nutrient levels

This topic contains 6 replies, has 5 voices, and was last updated by  Miyaruman 11 months ago.

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  • #2428


    Hello everyone!
    I started my spirulina culture, here in Italy about two months ago and everything seems to be going sort of ok. I guess the temperature and sun exposure have some sort of effect.
    I have a mother culture of about 100 mL that I every two weeks I empty out the contents into another 100ml flask and fill both up with a nutrient mix of water and Bicarbonate.

    First question:
    What carbonate concentration is needs to be added per L of water to achieve a pH of 9?
    – yesterday I saw that my nutrient solution was actually acidic (pH 6 – yeah I know! Newbie here :/) so I started adding Sodium bicarbonate and only achieved a ph of 9.

    Second question:
    Is there a difference (pros/cons) between using Sodium bicarbonate rather than Calcium carbonate? and related to that is there a difference (between the two carbonates) in concentration to be applied?

    Now, the contents of the second flask tend to be a bit more yellowish, so I add chelated iron to the culture.

    Third question:
    What concentration of chelated iron should be added and how often?

    On the note of the yellowish color, there are also yellow “clumps” on the bottom and I was wondering if I need to remove those, or there harmless? (I would assume that they could be used as nutrients, but not sure)

    Any help is well appreciated! Thank you and sorry if you cringed at my nutrient solution being pH 6, I’m trying to gear up and have all parameters in check, but need help/suggestions from Spirulina veterans like you guys!


  • #2442


    hey there. you need a concentration of 16.6g of sod bicarb per litre. which is about 8.2-8.5 ph depending on the purity. 2. if you were to use 16.8g of calcium carbonate instead of sod bicarb you’d have a lot of calcium in the medium which could cause toxicity and also salt precipitation when you add other nutrients like phosphates and sulphates. Sodium bicarb is by far the most efficient method to supplement co2. 3. the culture becomes yellowish because of lysis of cells, it will also start to emit a stronger pondy smell which will further get worse. there could be a lot of reasons to this (not only iron deficiency). best is to always have a few backups. But the optimum iron concentration is 0.01-0.02g/L of FeSO4. in my opinion it is better to use standardised chemicals than iron nails soaked in vinegar or anything of that sort.
    A little bit of sediment is nothing to worry about but if you have a lot of it, it can prove to be a haven for other microbes which you do not want in your cultures.
    Looking forward to hear from you, Brian 🙂

  • #2469


    Hello Miyaruman,

    I’m from Italy too, and i would like to start a home cultivation. Where do you found your spirulina alive?

    Thank you.

  • #2479

    Dr Cath

    @zenzeros try to reach out to Miyaruman. He’s also in Italy.

  • #2486


    Hello Miyaruman,
    I’m from Italy too, and I’m starting with a Spiruline culture. Finally I found spirulina in french site, and I Think will arrive in few days. I hope in good and alive state. 🙂
    I had many doubts about zarrouk mix because because I have no knowledge of chemistry, but surely in this forum we will find many answers. At the moment I bought a zarrouk mix but the instruction told that is not for human consumption. I’m starting with this, but I hoope to find a correct zarrouk.
    Let me know how it’s going your own cultivation.

  • #2499


    First if all thanks everyone for answering.

    At Brian – thank you for the valuable information. I’ll keep everyone updated on the progress.

    At Zenzeros and GC – I got my Spirulina from a French site. It just got here yesterday and I’m following the instructions in order to start a 1L culture but need to dechlorinate the water over night (or a couple).


    1. Is it necessary or recommended to have circulation throughout the night?
    – at the moment I have a small pump to provide the circulation.

    2. @ Brian (or anyone else) – would an organic fertilizer for growing crops be sufficient for providing the nutrients and how much would I add and how often. Any tips/rules in order to double up the quantity of Spirulina?

    That’s it for now – thanks and happy culturing!!

  • #2509


    Hello everyone,

    So I have started a new culture from a kit I obtained from France and it is designed to grow Spirulina for a 10 L volume. Meaning once I reach 10L I would have to sustain the culture with my own growth medium, or buy it again from the website.

    As you can tell from the picture the culture is doing quite healthy. I opted in keeping the 1L culutre in a small container and have it placed inside a tank with water so that I can heat the water around it in order to keep the optimal temperature for growth.

    The small container will probably take a maximum of 2L and then I would have to “grow” my courage and put it in the tank itself. I’m just concerned of contamination and the spirulina apocalypse. 😉

    I’m keeping the water circulation during the day with an air pump through an airstone and the temperature at 26-28 C. At night I turn off the aeration off and turn down the temperature at 22/23 Celsius.

    My question is when do I need to add/change water and nutrients to this 1L culture?

    Any help is very well appreciated!

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