Re: K+

[Thomas Barr <tcbiii at earthlink_net>]

> Quiz:
> 1) 1 g of Potassium in 200 L of water gives you how many mg/L of Potassium?
> A: 1000 mg/200 L = 5 mg/L = 5 ppm
> 
> 2) 1/4 tsp. of Potassium in 55 gallons of water gives you how many ppm of
> Potassium?
> A: I have no idea.

1/4 teaspoon K2SO4 = 2x39.1g/mole / 174.2 g/mol = about 45% K+. 1/4 teaspoon
average level weight= 1.67 grams x 45% = .75 grams of K. 0.75 grams = 750
mg.
The molar weights are approximate. Don't have a periodic chart sitting here.
Doesn't matter than much if your teaspoons are differentor if you are off a
little bit. A little high or a little low on K doesn't amount to a hill of
beans.  
Same can be said for NO3. + or - 1ppm doesn't make a difference with NO3 or
K or CO2.   

750 milligrams of K+ added to 55 gallons of water (not tank size) = 55
gallons x 3.785 liter per gallon= 208 liters; 750mg K+/208liters = 3.6ppm of
K (+ or - about .5ppm or so-nothing to worry about!). So adding 1/2 teaspoon
to an average 55 gallon tanks will give you about 45-50 gallons of water=>
170 to 190 liters.
Now you have about 4ppm or a tad over per 1/4 teaspoon.
Add 1/2 teaspoon for 8ppm. Adding KNO3 2-3x a week at 1/4 teaspoon each time
will add about another 700mg per 1/4 teaspoonful each time. So then you have
close to 16ppm or so of extra K added each week. Do a 50% water change and
this will leave you with about 20-40ppm range over time since a build up in
the water will remain but not too much if you do regular water changes. All
the K will not be used up by the plants so there will more than 0.0ppm and
then you are adding on top of that.
> 
> 3) How much Potassium Sulfate does your 55 Gallon plant tank need?
> A:  A big pinch every couple of days.  Try more or less and see what
> happens.

1/2 teaspoon every week if you also add KNO3 etc. More if you you do larger
than 50% water changes etc.
Regards,
Tom Barr