Potassium dosing

Stephen Wright

New Member
11 Nov 2019
U. K.
Hi folks please could you confirm if I've got my numbers correct for the following scenario.
I have a 60 L planted aquarium which is low in potassium. I need to raise the potassium content by approximately 14 parts per million (incrementally of course).
I'm using potassium gluconate tablets and each one contains 90 mg of potassium.
I've calculated that I need to add 9.3 tablets in total to to increase the potassium level by 14 parts per million.
Does this sound right please?
Many thanks in advance.


7 Apr 2008
nr Bath
Hi all,
Welcome Stephen. We have a lot of threads on UKAPS, but I'm not sure any-one has ever asked that question before.
I'm using potassium gluconate tablets
They will do, but I'm going to assume that is a very expensive option.

Nearly all potassium compounds are soluble, so you can use a, much cheaper, simple salt. People normally use potassium nitrate (KNO3), or dipotassium phosphate (K2HPO4.6H2O) etc, because you get a plant nutrient from both cation (K+) and anion (NO3-) etc. Have a look at <"Aquarium Plant Food UK"> or <"Amazon"> etc.

Potassium chloride (KCl) is probably the cheapest option.
I need to raise the potassium content by approximately 14 parts per million (incrementally of course).
You good in one go, you don't need to raise it incrementally. That is a really small addition of ions.

The maths looks about right, you've added just under 1 gram of K, which is approx. 1000 (1*10^3) milligrams, and milligrams per litre is equivalent to ppm. 1000/60 is about 15, so I'll assume that your more exact calculation gives you 14ppm K.

cheers Darrel


30 Jun 2011
Yep, the maths look right to me too. BUT that's assuming that 60l is the actual water content of your tank. If it's a nominal '60l' tank as described by the supplier, you may need to allow for the substrate, hardscape etc displacing some water, as you seem to be trying to get a very exact concentration.
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