# Preparing stock solution for EI dosing. Which is right?



## Zak Rafik (6 Jul 2015)

Hi everyone,

I'm in the process of preparing some stock solution as part of my EI dosing. 
Can someone clarify which is the right method in making the stock solution.
Please note the below mentioned quantity is just for example sake.

Scenario:
According to an on-line fertz calculator, I was informed to mix 70 grammes of X salt into water which should give a 500ml of final stock solution.

Question:
*A*: Do I take 70 grams of X salt and mix with *500 ml* of water

OR

*B*: Do I take 70 grams of X salt and mix with *430 ml* of water.

All this while I have been mixing 70 grammes into 500ml water but recently someone informed me that, he lessens the 70 grams ( approx 70 ml) from the 500ml. That is 70 grams + 430 ml water.

Please inform.
Cheers.


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## xim (6 Jul 2015)

The correct answer is mixing the 70 grammes to make the 500ml of final stock solution.
IE, mix the 70 grammes to...for example, 300ml.
Then, after it is all dissolved, add more water to make it 500 ml.



Zak Rafik said:


> *A*: Do I take 70 grams of X salt and mix with *500 ml* of water



This will end up with more than 500 ml solution. And will make you dose less frets than what you calculated.



Zak Rafik said:


> *B*: Do I take 70 grams of X salt and mix with *430 ml* of water.



This will probably end up with less than 500 ml and make you dose more than calculated. Because you dose by ml, not weight.

But the error margin of EI is large. I mean the error from this example is not enough to make or break your tank situation.


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## Zak Rafik (7 Jul 2015)

xim said:


> The correct answer is mixing the 70 grammes to make the 500ml of final stock solution.
> IE, mix the 70 grammes to...for example, 300ml.
> Then, after it is all dissolved, add more water to make it 500 ml.
> 
> ...



Awesome. Thanks.


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