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Re: K2PO4 vs KH2PO4

Travis wrote:

>I bought the wrong stuff. I know I should have ordered K2PO4 instead of
>KH2PO4 for dosing potassium. I have KNO3 for dosing nitrate. I know I can
>use KH2PO4 for phosphate dosing, but what should I do about K-potassium
>dosing? Should I just assume the plants are getting enough from the
>KH2PO4-mono potassium phosphate and KNO3-potassium nitrate?

Did you mean K2SO4 (potassium sulfate) for potassium?  Potassium phosphate 
isn't a good source of K+.

Anyway, you'll not get appreciable K+ from KH2PO4, but you can get a fair 
amount from KNO3.  Use Chuck Gadd's dosage calculator to determine how much 
-- http://www.csd.net/~cgadd/aqua/art_plant_dosage_calc.htm. If you dose 
dry KNO3 directly into the tank, just put 1 in the "Amount of water to mix 
with" box.

Still, it's doubtful you'll get enough K+ from KNO3 alone.  In addition to 
the potassium that comes from KNO3 doses, I add around 10ppm K+ via K2SO4 
after the weekly water change.
Chuck Huffine
Knoxville, Tennessee