Urea

Urea based aquatic plant fertilizing is becoming more popular lately while not having enough supporting information. I have added this page describing urea recipes, calculations, ratios and other necessities.

Urea (carbamide) is an organic compound with the chemical formula CO(NH2)2. It is highly soluble in water and practically non-toxic to mammals and aquatic life. It is about thousand times less toxic than ammonium nitrate NH4NO3. Dissolved in water, it is neither acidic nor alkaline. It will slowly release ammonium NH4 and degrade to nitrate NO3. Ammonium is more toxic to fish, however, ammonium release is slow making urea much less toxic than ammonium salts. Urea is widely used in terrestrial fertilizers and also in commercial aquarium fertilizers from ADA and Seachem. In applications with aquatic fauna careful planning is necessary.

FAQ

What are the necessary prerequisites to use urea safely?

pH

Water pH must be < 7. In pH > 7 ammonium NH4 becomes toxic ammonia NH3.

Biological filtration 5 – 10% of aquarium size

In order to detoxify remaining ammonia NH4 and nitrite NO2 to relatively harmless nitrate NO3 the biological filter media need to be at least 5% of the aquarium size.

Established biological filtration

Aquarium biological filtration should be fully cycled to convert ammonia NH4 to nitrite NO2 and to relatively harmless nitrate NO3.

Why dosing urea?

Urea fertilizer additions make plants explode, pearling even at night and growing fast. Urea is taken by plants easier and faster than NO3. Also, urea includes carbon C, the carbon we dose CO2 for.

Why urea instead of ammonium nitrate NH4NO3?

Urea is about thousand time less toxic than ammonium nitrate NH4NO3.

urea LC50

16 000 ppm, Harlequinfish red rasbora, Rasbora heteromorpha

11 253 ppm, Guppy, Poecilia reticulate

10 000 ppm, Carp, Leuciscus idus melanotus

9 100 ppm, Barillius barna fish

http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC35157

ammonium nitrate LC50

1 ppm, Rainbow trout, Oncorhynchus mykiss

77 ppm, Carp, Cyprinus carpio

http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC33852#Ecotoxicity

How to prepare and dose urea fertilizer?

Why urea ppm as NO3 equivalent?

What do these have in common?

0.23 ppm nitrogen N

0.29 ppm ammonium NH4

0.48 ppm urea CO(NH2)2

0.65 ppm ammonium nitrate NH4NO3

1.00 ppm nitrate NO3

All represent the same nitrogen N concentration.

When, in this hobby we talk about nitrogen N in fertilizers we usually use nitrate NO3 to express concentrations. However, some fertilizers containing ammonium nitrate NH4NO3 or urea CO(NH2)2 use ppm of ammonium nitrate or ppm of urea, and some list ppm of nitrogen. How do they correlate in terms of nitrogen N? Not easy task. We need to bring some common language. Why not use ppm of NO3 equivalent since we are so familiar with it?

For example, an aquarium is receiving a daily dose of 1 ppm of NO3 in form of KNO3. If I was going to change it to urea based fertilizer, I would use the same 1 ppm of urea as NO3 equivalent to match the previous nitrogen concentration.

PPS-Pro Urea solution #3 can be used as a direct KNO3 substitute because it has the same potassium K and nitrogen N concentrations as KNO3.

Can I switch back and forth between PPS-Pro and PPS-Pro Urea fertilizers?

Yes, both are compatible in strength and dosing quantity.

PPS-Pro

Solution #1 macros

Solution #2 micros

PPS-Pro Urea

Solution #1 KNO3 Free macros

Solution #2 micros

Solution #3 KNO3 sub by Urea

Why is recommended nickel Ni when using urea?

Because plants need nickel Ni in order to process urea fertilizer. It is widely available in tap waters but may not be sufficient in RO/DI water. Some trace element products do not include nickel, like CSM+B and Micronutrient Mix EDTA+DTPA. However, both can be modified to Upgraded CSM+B EDTA and Micronutrient Mix EDTA+DTPA, please see recipe.

How to convert between nitrate NO3 and nitrogen N?

NO3 = 4.4267 x N

N = 0.2259 x NO3

How to convert between nitrate NO3 and ammonium NH4?

NO3 = 3.4373 x NH4

NH4 = 0.2909 x NO3

How to convert between nitrate NO3 and urea CO(NH2)2?

NO3 = 2.0649 x CO(NH2)2

CO(NH2)2 = 0.4843 x NO3

How to convert between nitrate NO3 and ammonium nitrate NH4NO3?

NO3 = 1.5493 x NH4NO3

NH4NO3 = 0.6455 x NO3

How to convert between nitrate NO3 and potassium nitrate KNO3?

NO3 = 0.6133 x KNO3

KNO3 = 1.6306 x NO3

How to convert between nitrogen N and urea CO(NH2)2?

N = 0.4665 x urea

urea = 2.1438 x N

How to convert between nitrogen N and ammonium nitrate NH4NO3?

N = 0.35 x NH4NO3

NH4NO3 = 2.8573 x N