# potassium meter Mg/L or ppm?



## jblasto (Jan 4, 2013)

I got a potassium meter from Hanna instruments to read my planted tanks water content and the reading displays in Mg/L 

I don't quite understand the conversion of that to ppm or if that is ppm? Can someone help me understand how to read it. Thanks.


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## emc7 (Jul 23, 2005)

Its not 1:1 but its in the same order of magnitude as ppm. So how accurate do you need to be? a g of water is 1 mL at STP, so 1 mg of water in 1 L is is 0.001 mL / L or 1 mL in 1 million mL. Potassium doesn't have a density of 1, but you should be able to look up the density for the potassium salt you add (KCL or KSo4) and use the correction factor. KCl & KOH are both about 2 g/mL. So divide by 2. Its isn't exactly accurate, but it should be close enough. What you really need is consistency. So you can tell if you K+ is suddenly low and you need to dose.


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