EI - getting by without KNO3


Junior Poster
Sep 3, 2007

I am about to start EI dosing, and I went shopping at aquariumfertlizers.com. I live outside the US, but the shipping offered is extremely reasonable, so I went for it.

One problem of course is that we cannot buy KNO3, and have to source it locally. I eventually did but it added $20 and a few hours of search time, not to mention having to spend a day at home waiting for delivery.

I noticed that Ca(NO3)2 is easily available on the aquariumfertilizers.com and cheap to boot. So it got me to thinking, once you have Ca(NO3)2 It must be easy enough to get by without KNO3 in the first place.

Basically you would have to add less Ca++ at GH booster time, and make up the lost potassium with something else like K2SO4. I don't know exactly what is in GH booster, so I worked out a simple CaSO4/MgSO4 mix instead.

In a high light setting where you are adding 40 mg/L per week of NO3 as per Greg Watson's EI light, this means that you would not need to add and CaSO4 at all, becaues you would get all the Ca++ you need form the CaNO3.

I have a low light, soft water tank, so I am only planning on adding about 15 mg/L per week (1/4 tsp KNO3 3x/week), but still the same amount of GH booster.

A lot of maths follows which I invite those wiser than me to check. It is kept as precise as possible until the very end when working out approximate teaspoon doses.

The bottom line for my lowlight 200L tank:

Add 1/4 tsp MgSO4 + 3/8 tsp CaSO4 instead of 1 tsp GH booster
Add 1/4 tsp of Ca(NO3)2 + 1/8 tsp K2SO4 instead of 1/4 tsp KNO3

Here's the working out (long)


EI for a low light soft water tank I would add:

2 dH of GH in a ratio of 1/5 Mg++ and 4/5 Ca++
15 mg/L of NO3- from KNO3
9mg/L of K+ from KNO3

2 dH is equivalent to 36.7 mg/L CaCO3

Of this 7.34 mg/mL to come from Mg
And 29.4 mg/mL to come from Ca

Equivalent weight of Ca = 20.45
Equivalent weight of Mg = 12.15
Equivalent weight of CaCO3 = 50.045
Ca/CaCO2 Ratio = 0.4086
Mg/CaCO2 Ratio = 0.2428

Ca++ to add is 29.4 x 0.4086 = 12.01 mg/L
Mg++ to add is 7.34 x 0.2428 = 1.78 mg/L

Nitrate from Ca(NO3)2.2H2O

Ca(NO3)2.4H2O contains 17% Ca and 52.5% NO3
Adding 15 mg/mL NO3 requires 15/0.525 = 28.6 mg/L
Compared to KNO3 it leaves a deficiency of 10mg/L K+
And a surplus of 28.6*0.17 = 4.87 mg/L Calcium

Ca from CaSo4.2H2O

To get to 12.01 we need a further 7.22 mg/L Ca from somewhere else
Ca++ makes up 23.2% CaSO.2H2O
Therefore need to add 7.22/0.232 = 31.1 mg/mL of CaSO4.2H2O

K+ from K2SO4
We need to add 9 mg/L of K+ from somewhere else
K+ makes up 39.1% of K2SO4
Therefore we need to add 9/0.391 = 23.1 mg/mL K2SO4

Magnesium from MgSO4.7H2O
We need to add 1.71 mg/L Magnesium
Mg makes up 9.86%
Therefore need to add 1.78 / 0.986 = 18.1 mg/L

200L Tank:

GH Boost Day
CaSO4: add 200L x 31.1mg/L = 6.22g
MgSO4: add 200KL x 18.1 mg/L = 3.62g

"KNO3" Day
CaNO3: add 200L x 28 mg/L / 3 = 1.86g
K2SO4: add 200L x 23.1 mg/L / 3 = 1.7g

Now, finally to get it all into EI friendly APPROXIMATE teaspoons

Density of MgSO4.7H2O 1.7g/mL therefore add 2.13 mL = 1/4 Tsp
Density of CaSO4.2H2O = 2.32 g/mL therefore add 1.93 mL = 3/8 Tsp

Density of Ca(NO3)2.4H2O = 1.86 g/mL therefore add 1mL ~ 3/16-1/4 of a teaspoon
Density of K2SO4 = 2.66 g/Ml therefore add 0.63mL = 1/8 Tsp


Lifetime Members
Lifetime Member
Feb 13, 2005
Chandler, Az
Timmo, I am not sure where you live but here in the US another cheap source of KNO3 is sold as stump remover. Perhaps this is available wehre you are at as well?


Junior Poster
Sep 3, 2007
I asked for stump remover in an Australian hardware store and they just looked at me blankly. Maybe its because this is the country that gave the world the stump-jump plough. Dunno about that tho.


Guru Class Expert
Jan 22, 2008
Vista, Ca
timmo when you say hardware do you mean a tool shop or a home depot, you most likely need to find a place with a garden/outdoor section. I also agree with nick above, any farm supply house that sells to the public sells nitrogen in large bags, you may be able to score a lifetime supply for cheap..


Timmo, have you tried to get E252 at some spices shop/online? I got some that way when it became impossible to get it any other way.

I could imagine Australia is perhaps like where I live. Because of 9/11 and the following terror in England/Spain/almostGermany there is no way to get KNO3 for a private person anymore but in very small quantities and to exorbitant prices at pharmacies. Some pharmacists will not sell to no one, period (they are afraid to get sued if something bad happened). Home depot like shops won't sell it. Farmer's shops will not sell to not farmers (I asked there, that man laughed at me).

Just for your information that outside the states it might be ... difficult.


Jan 24, 2005
Melbourne, Australia
Timmo, where in Australia are you located? As there are a number of places where you can get KN03 but it's not something that can be posted as it is classified as a corrosive agent.


Junior Poster
Sep 3, 2007
ccLansman;35033 said:
timmo when you say hardware do you mean a tool shop or a home depot, you most likely need to find a place with a garden/outdoor section. I also agree with nick above, any farm supply house that sells to the public sells nitrogen in large bags, you may be able to score a lifetime supply for cheap..

As a previous poster has said, the world outside the United States is different

I think the closest equivalent to Home Depot in Australia is Bunnings - it has a big big garden section, I asked there about ANY source of KNO3 to a guy who was otherwise helpful. I told him why I wanted it, and he knew exactly what I was talking about and said "you just won't be able to get it"

I have not tried farm supply shops as I live in the middle of Sydney and so far as I know you won't find them here. If you lived rurally and they knew you well, MAYBE they would help you.

Personally speaking I have found some KNO3, but it was not especially cheap, and involved an separate order, and staying home 2 days waiting for it to show up.


PS - the point of this post was exploring ways to get by without KNO3. No-one has really said either way if the above adds up.


Guru Class Expert
Jun 8, 2007
Just wanted to say that I feel your pain. :) I live in a remote part of Canada, and many things are either not locally available or available but very expensive. To me, part of the challenge and maybe part of the fun is learning how to get by without having the same things available as other people do and without spending a fortune trying to do things exactly the same way as everyone else just because nobody has figured out a different way to do it.

So bottom line is that I would try to answer your question if I wasn't so bad at math. :)

Just to round out my post with a couple of cliches: There's more than one way to skin a cat, and necessity is the mother of invention. :)