UREA (Nitrogen Fertilizer) 400 gram

(1 customer review)


Short information

To use as nitrogen fertilization in Spirulina culture or other gardening and farming. Easy to use and enough to grow a lot.

Amount: 400 gram (0.88 lbs)

N-P-K ratio: 46-0-0 (46% nitrogen)

Chemical formula: CO(NH2)2 / CH4NO2

Density: 1.32 kg/L

Composition: Small round granules

SKU: A-S007-0400 Category:


Why grow Spirulina with Urea?

Urea makes spirulina grow faster and with a higher protein yield than with nitrate (NO3) in the normal nitrate-based mediums:

–         The intra-cell mechanisms need to use less energy when utilizing Urea and can instead use that energy to grow,

–         It is more nitrogen dense (46% vs circa 20% for nitrates) and

–         The rest of it is converted into CO2 – which gives the Spirulina more carbon to grow from.

–          Spirulina can take a higher concentration of ammonia than other organisms, and since Urea is broken down to ammonia, added Urea can work as a culture cleaner at the same time as it gives nitrogen.


However, in too high concentrations Urea will kill your Spirulina culture, contrary to the normal nitrogen source, nitrate (NO3-), which Spirulina is not so sensitive to. So, supply it continuously in low amounts and you will get greater growth yields and harvest more protein-rich Spirulina.


General information about Urea

Urea is the molecule the body disposes of nitrogen as via the urine (most from protein with its amino acids that are broken down to ammonia and then turned into Urea). It is the most nitrogen dense fertilizer you can find. In water, it will, over hours to days, break down into two ammonia (NH3 or NH2-) and one carbon dioxide (CO2) molecule, which will give the culture a good boost of nitrogen (N) and carbon (C) – the two elements growing Spirulina needs the most and what a culture often is first to use up.

With the right amount and correctly used Urea, your Spirulina culture can grow even better, and get a higher protein content, than now with your nitrate growth medium.

This Urea can of course also be used as a soil or hydroponic fertilizer.


Urea as a fertilizer for plants and soil usage

This Urea may also be used for other fertilizing applications in gardens and farming. Spread out over the whole growing season, and depending on the crop, use between 20 to 70-gram Urea per square meter (m2), or 200 to 700 kg per hectare (190 to 660 pounds per acre). Apply more in the late spring and early summer months and less or none in the later growing months. During flowering and fruiting (later in the season) a plant will in general stop absorbing nitrogen. Therefore, Urea could be wasted to no gain if applied then. To apply all required Urea at once will cause toxicity so apply at most 10 to 12 gram per square meter and month. It is also possible to dissolve the Urea in water and spray it on the plant foliage. However, do so with care since a too strong mixture will burn the plant. Apply more to the soil during dry conditions and less under wet. Dig down the Urea into the soil as it dissolves to ammonia in water after one day or less (depending on temperature). Tests have shown that up to 25% of the nitrogen in the Urea can be lost via ammonia evaporation if applied on the surface in the wrong way. Also, do not apply the Urea near seeds or plants to avoid ammonia toxicity and damage.


More on Urea and Spirulina culturing

Use this fertilizer to supplement the Spirulina culture with more nitrogen (N). Besides CO2 the second most required nutrient for Spirulina growth is nitrogen. Nitrogen is also often what is the lacking component in a growing Spirulina culture. But it is also what in excess can kill the culture. So, you need to add it regularly but is small amounts.

You can either add nitrogen as nitrate (NO3), ammonia/ammonium (NH3/NH4+), Urea or larger nitrogen molecules such as amino acids. Nitrate is easier and less harmful in higher concentrations but also less well used by the Spirulina. Since nitrate mostly is made out of oxygen very little of the weight is nitrogen (circa 22%). Nitrate also comes as a salt with a corresponding ion (K+, Ca2+, Mg2+, Na+ etc.) which decreases the actual nitrogen percentage even more (down to circa 15%). These ions will also accumulate and in the end cause a lower growth rate. An exception here is ammonium nitrate (NH4NO3) which is about 35% nitrogen. However, with ammonium nitrate, you cannot add as much as wanted direct due to the direct ammonium toxicity. So here Urea will work as a great replacement instead to nitrate with a much higher concentration of nitrogen. Since everything of the Urea will be absorbed (N, C, and O) you can also feed it over a long period without any risk of buildup of any other elements.


Urea to add per volume of culture

The culture density and strength are important factors for deciding how much Urea you can add to your culture. The more Spirulina cells there are (density) the more ammonia (which the Urea breaks down to over hours to days) the cells can absorb. Also, the faster the culture grows (strength) the more ammonia from the Urea it will absorb and use. So, if you have a slow-growing and not so dense culture you cannot add as much as if it was dense and fast growing. On the product bag you will get more guidance of usage but if you are unsure about your conditions it is always better to add less then more to your Spirulina culture. A sign that you have added too much is that the culture starts to smell ammonia. When this happens, you should stop adding Urea for some time until the stench is gone. To get rid of the ammonia smell faster you can increase the bobbling and dilute the culture with more medium. This will gas away the ammonia faster and decrease the total harmful concentration. If you here want to be really cautious you can filter out the Spirulina and add it to a new fresh medium without Urea.


The absolute maximum concentration of Urea per liter you should use is 0.5 grams (0.5 g/L or 0.067 oz/gallon). But this is for a very tolerant and strong culture and you cannot do this every day. Always start with much less if you are unsure.

This 0.5 gram per liter equals 0.23 gram of nitrogen per liter culture and if all was absorbed it would give you 2 gram (0.071 oz) Spirulina (dry weight). However, since ammonia easily is gassed away studies have shown that actually only circa 20% of the nitrogen in the Urea will be absorbed into the Spirulina when doing this. This means that the highest concentration will give you circa 0.5 gramSpirulina (dry weight) per liter from the nitrogen in the Urea. However, if you add Urea continuously in smaller amounts when the Spirulina absorbs the ammonia faster more will be used and less will be gassed away. This is also less harmful to your culture. For a dense fast growing culture, you can add 0.05-gram Urea per liter every day (0.05 g/L/d). For a thin and slow growing culture, add a maximum of 0.005 to 0.01 gram per liter and day (5-10 mg/L/d). Smell the culture before you add any Urea and increase it every day as the description on the package.

Best is to add Urea regularly (once or twice every day) to your culture. This maximizes the direct usage of Urea and there will be less risk of an extended nitrogen deficiency, that cause the Spirulina to stop growing.


Table for continues addition of Urea to a culture

Use the following table to decide how much Urea to add. If you by any means smell ammonia in the culture, then stop adding Urea and follow the descriptions above. The figures are set as a general estimate so be aware that they still can be too high for your culture.

Metric system Urea feed table

  Gram Urea to add per liter culture and day (g/L/d)
Density (mm) Growing (g/L/d) Slow growing (g/L/d) Not growing (g/L/d)
5 0,26 0,051 0,026
10 0,13 0,026 0,013
20 0,064 0,013 0,0064
30 0,043 0,0085 0,0043
40 0,032 0,0064 0,0032
50 0,026 0,0051 0,0026
60 0,021 0,0043 0
70 0,018 0,0037 0
80 0,016 0,0032 0
90 0,014 0,0028 0
100 0,013 0,0026 0
150 0,0085 0 0
200 0,0064 0 0

US customary system Urea feed table

  Ounces Urea to add per gallon culture and day (oz/gal/d)
Density (inch) Growing (oz/gal/d) Slow growing (oz/gal/d) Not growing  (oz/gal/d)
0,20 0,034 0,0068 0,0034
0,39 0,017 0,0034 0,0017
0,79 0,0085 0,0017 0,00085
1,18 0,0057 0,0011 0,00057
1,57 0,0043 0,00085 0,00043
1,97 0,0034 0,00068 0,00034
2,36 0,0028 0,00057 0
2,76 0,0024 0,00049 0
3,15 0,0021 0,00043 0
3,54 0,0019 0,00038 0
3,94 0,0017 0,00034 0
5,91 0,0011 0 0
7,87 0,00085 0 0


Product content: Urea (CH4N2O) – (N:P:K ratio 46:0:0)


Delivery time

Delivery to EU is done within 5-10 days and to the rest of the world within 10-15 days.


About the seller

HealthAlgae Sweden AB, aka HealthAlgae, is a Swedish company producing healthy, clean and secure algae for human and animal consumption.


Thank you and great Spirulina or crop cultivation!


And remember,

You can always ask us for tips and help. We want this to work for you so we are glad to help. Just send us an email at “order – at – healthalgae dot com”


HealthAlgae return policy:

HealthAlgae accepts returns within 2 weeks of receiving your order.


HealthAlgae refund policy:

HealthAlgae gives refunds when we cannot help you in regard to your order or if you are dissatisfied with your purchase. We will try to make as much as possible for you to succeed.

Additional information

Weight 1 kg
Dimensions 15 × 15 × 13 cm

1 review for UREA (Nitrogen Fertilizer) 400 gram

  1. Thobias (verified owner)

    Didnt get it although the mail said so.

    • Marcus (store manager)

      Dear Thobias,
      Thank you for your feedback. I have contacted you and now know that you have received this urea nitrogen fertilizer for the Spirulina culture and the Spirulina medium. Sorry about this and I understand your feedback.

      Best regards,

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