Please check my math.

[SparKy697]

I know I'm probably beating this thing to death, but I really just want to understand what I'm doing rather then just following a recipe.

Using Chucks calculator I have come up with these values:

I'll just take Potassium as an example.

Mixing a solution of 10 tsp into 500 ml of water gives me a solution. And if I add 1 ml of this solution to a 29 gallon tank it will raise the concentration of K by .49 ppm.

Now, as far as dosing this into the tank. If my target is 20 ppm in the tank, and for this explanation we say that there is 0 ppm in the tank, should I add 41ml (20ppm/.49ppm = 40.81) three times a week? Or am I adding 13.6 ml three times a week (1/3)?

 

[rkilling1]

You would add 41 mls three times a week, if 20 PPM K was your target. Assuming you have high-light, CO2 and a high plant mass. ie EI dosing

If you are adding KNO3, you also have to take into account the K from this aswell.

 

[SparKy697]

If you are adding KNO3, you also have to take into account the K from this aswell.

THANK YOU!!!!!

That info right there was the missing link. Reading some of the recipes in other threads I just could not rationalize some of the recommended doses.

I have to go and find a way to put some of this hair back in my head now.

Thanks again.


EDIT:

I found a spreadsheet from Tom Barr that helps with this calculation too. Man, I must have spent half the day trying to find a definitive answer on the net about this. None of the articles made this clear to me in the least.

So I don't know if I was just getting tunnel vision because of frustration, or maybe this might be worth spelling out a little more in an article?

 

[malkore]

I don't recommend a dosing solution for potassium. You dose too much, too often, to make a solution worth your while.

Just add a half teaspoon to the new tank water after a water change (or whatever dry amount gives you 15ppm in 29gal of water).