# How much potassium to add for EI?



## fishstein (Dec 12, 2005)

The plants in one of my tanks, a 75 gallon, which I've kept with great success up to now, seem to be suffering from a Potassium deficiency, which would make sense as the plant density has increased and I haven't been adding an extra source of K. Up to now I've added 3/4 teaspoon Potassium Nitrate and 1/4 Mono Potassium Phosphate every other day, Seachem Flourish 7.5 ml on the other days. How much Potassium Sulfate should I add? I read somewhere on the forum that I should be adding 1/4 teaspoon together with the Potassium Nitrate and Mono Potassium Phosphate.


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## hoppycalif (Apr 7, 2005)

If you rely on KNO3 and KH2PO4 for nitrates and phosphates you shouldn't need any more potassium. Plants' requirement for potassium isn't for a cut and dried specific amount, so there should be enough from the other two chemicals. But, more isn't harmful, so you could add a dose of K2SO4 equal to the KH2PO4 dosage along with the other chemicals.


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## fishstein (Dec 12, 2005)

Hi Hoppy, 

Thanks, that's exactly what I read in another post. I never thought I'd need K2SO4. I've been using KNO3 and KH2PO4 for years, and never seemed to have a problem, but then again I've been growing more fast growers recently and I have more light, higher quality light and better CO2 diffusion and I noticed a clear potassium deficiency. 3/4 KNO3 and 1/4 KH2PO4 3 days a week, and Seachem Flourish 7.5 ml 3 days a week, has not been meeting the Potassium needs of the plants. Hopefully the 1/4 teaspoon K2SO4 will help.


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## xjia (Sep 19, 2006)

adding more k2so4 does no harm....


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## Glouglou (Feb 21, 2006)

More is not always better and experienced aquarists and scientific paper will warn about problems with overdose of potassium.

Overdose of anything is never a good thing.

Wish we can have cheap pottasium test kit!

Somebody try these guys...http://www.petsolutions.com/default.aspx?ItemId=12516807&EID=12516807&SID=FROOGLE

I'm trying hard to develop one myself.....


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## Angry the Clown (Aug 26, 2006)

Chuck's Calc has a suggested target of approx. 20ppm K. in a 75 gal, 3/4 tsp of KNO3 adds about 5.7 ppm K. The K in the Phosphate is negligible. Another 1.5 tsp of K2SO4 is needed to add another 14 +/- ppm of K. This ratio of 3:1:6 of N:K freaked me out at first, but I have come to deal with it.

My tank is heavily planted with crypts, and if I don't add enough K2SO4 I get a lot of pinholes in the leaves. I am curious as to what the effects of an overdose of K in a planted tank are.


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