Potassium Test Kit?

[Kalinkacat]

I was reading an article about achieving a flourishing plant tank and the author mentions that he was trying to achieve 20 ppm potassium.  I have the Hagen master test kit and there is no test for potassium in there.  Does anyone know where to get one or how to measure it?

Thanks,

[charlie]

As far as I'm aware there is no hobby grade test kit for Potassium, but quite possible it may be out there

[wolfiewill]

It's essentially the GH test kit.

[Kalinkacat]

How do you use the GH/KH kit to calculate Potassium?

[wolfiewill]

How do you use the GH/KH kit to calculate Potassium?

Simple: Test for GH first, add your source of calcium, and test again. An API test kit gives the GH units in both degrees and ppm (but for brevity - 1 degree of general hardness = 17.9 ppm). Also, and probably more importantly, your tap water probably provides plenty of calcium. If you are on city of Ottawa water the calcium content out of the tap is 16 ppm, and the GH is in the 2.5 to 3.0 degree range. All that is needed is to raise the GH to four or more and you'll have plenty of calcium. I use the PPS method of fert dosing and so do infrequent water changes. But when I do I add Seachem Equilibrium to put the GH at or over 4 right after the WC. This ensures I have enough calcium for my plants for many weeks. And, if you use the EI approach to dosing, do nothing. The water from your tap has enough, and will be replenished each week when you do your 50% WC. If you're on well water somewhere in the Ottawa Valley, your calcium content is probably very, very high and won't need to be increased..... ever!.

[Kalinkacat]

So Potassium is Calcium?

My Hagen test kit gave me a Calcium level of 40 and a CaCo3 of 100 after a 50% water change - no ferts or co2 added.  What does that correspond to in Potassium?  What Calcium/CaCo3 numbers should I be aiming for?

[charlie]

As far as I'm aware there is no hobby grade test kit for Potassium, but quite possible it may be out there

It appears that my belief of no hobby potassium test kit is available is untrue.
Elos does
m.drsfostersmith.com/product/prod_display.cfm?pcatid=26779

[wolfiewill]

So Potassium is Calcium?

My Hagen test kit gave me a Calcium level of 40 and a CaCo3 of 100 after a 50% water change - no ferts or co2 added.  What does that correspond to in Potassium?  What Calcium/CaCo3 numbers should I be aiming for?

Sorry, I should have said 'to add your source of potassium' and then retest. My mistake. No calcium is not potassium. Sorry.