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Potassium (K)


  1. Rotala frustrations
    by Paul Sears <psears/> (Tue, 7 Mar 2000)
  2. Re:Optimum Potassium Level
    by krombhol/ (Paul Krombholz) (Sat, 29 Apr 2000)
  3. RE:K+ levels
    by "Thomas Barr" <tcbiii/> (Sat, 29 Apr 2000)
  4. RE: K+ test kits
    by "Thomas Barr" <tcbiii/> (Wed, 03 May 2000)
  5. Aquarium Landscapes, ADA & Potassium
    by "Roger S. Miller" <rgrmill/> (Sat, 6 May 2000)
  6. Potassium carbonate/bicarbonate
    by "Jamie Johnson" <jjohnson/> (Mon, 12 Jun 2000)

Rotala frustrations

by Paul Sears <psears/>
Date: Tue, 7 Mar 2000

> From: Ryan Mills <>
> Subject: Rotala Frustrations
> 30 gallons
> PH: 6.8
> GH: 90ppm
> KH: 4ppm
> Phosphates: .1-.2ppm
> Nitrates: 4-5ppm with addition of nitrate of soda
> 1.5 ml Flourish divided over the week
> .5 ml of Flourish iron per day
> 50 milligrams potassium gluconate per week
> - -small ammount of boric acid added per week
> - -normal gravel substrate containing some Flourish tabs
> and old laterite covered with flourite

	I think that you are adding an inadequate amount of potassium.
That 50 mg of potassium gluconate contains only about 8 mg of potassium,
and the 1.5 mL of Flourish probably contains less than 50 mg (what is the
concentration of K in it?).

	I have to add a lot more than that to keep _some_ plants happy,
and the effect of adding more K2SO4 to a tank can be quite dramatic
for plants that are doing really badly.  Rotala is one plant that will
not grow in my 160 L tank unless I add it.

> I got some Rotala macrandra at an auction a
> bit over a month ago, and while it took awhile to get
> going, it did well for a month or so, growing much
> larger and wavier leaves, even though the lower leaves
> would and still will not stay red.  I finally trimmed
> it, and the cuttings continue to grow; sort of.  The
> lower leaves of the cuttings have rotted away, with
> the tops growing and roots growing strongly.  The
> original patch has not kept growing, and like some of
> the cuttings, shows incredibly small and puny
> distorted leaves.

	That sounds consistent with my experience.

>  I followed some list people's
> advice on adding potassium, and this has worked to
> rapidly fix the Bacopa, but still not the Rotala.

	I'm pretty sure the plants compete for nutrients.
Some cope better than others with short supply of a nutrient.

	Add a gram or so of K2SO4.

- -- 
Paul Sears        Ottawa, Canada

Re:Optimum Potassium Level

by krombhol/ (Paul Krombholz)
Date: Sat, 29 Apr 2000

       From: "Ashley Sligh" <>
       Date: Sat, 29 Apr 2000 11:44:02 EDT

What is the optimal level of potassium for planted tanks?  Any one have any
potassium test kit suggestions?

~Ashley Sligh

If you get any cloudiness using the LaMotte potassium test kit, your plants
will be fine.  If you do not get any cloudiness, then it is time to add
more.  You can go up to at least 50 ppm potassium, possibly higher, without
danger to anything.

Paul Krombholz, in central Mississippi, where the trees are fully leafed
out, and all the summer birds are in place.  

RE:K+ levels

by "Thomas Barr" <tcbiii/>
Date: Sat, 29 Apr 2000

>What is the optimal level of potassium for planted tanks?  Any one have any 
>potassium test kit suggestions?
>~Ashley Sligh
>Aquatic Gardeners Association

20-30ppm with a LaMott kit. Aquarium Landscapes also makes a kit.
It's not one of those elements you should really worry that much about as
long as there's some in there. Excesses do not hurt IMO. Lack of it can slow
things down in high light tanks. I add about an extra 5-10ppm to my regular
dosing by way of estimating from the amount of water I have and the amount
of K+ I add after a water change. If I have a 20 gallon tank I'll about a
1/4 teaspoon of K2SO4 to it weekly plus the TMG etc which also has some in
there. If you add KNO3 this can another source and if you need a fair amount
this can be your only source also of K+. Riccia uses more of it than many
plants. You really don't need  a test kit the archives as
there's some info on this in there.
Tom Barr  

RE: K+ test kits

by "Thomas Barr" <tcbiii/>
Date: Wed, 03 May 2000

> They also have the only 
>Potassium Test Kit I have ever seen available. 

Lamott makes one too. Not a big deal to have a test kit for this element as
overdosing has never caused an algae outbreak in any tank I have heard of.
Rather than sweat and pay more for a product just use the K2SO4 like most
APD'ers. I add about 1/4 teaspoon(Green All-10lb bag about 4-5$= life time
supply) to every 35 gallons of water twice a week(sometimes more) and after
50% water changes. There is some K+ in my TMG and your fertilizer also. I
have about 20-30ppm or so typically when I test. I think adding about 5ppm
extra 2X a week seems about right but it's hard to really say. My plants are
certainly happier with the extra amounts of K+ but how much etc? I'm not too
certain but it's surely a large range and excess seems not to be an issue so
I add a fair amount. Wouldn't want any plants not getting their fill :) 

This is one test kit you do not need unless you have extra $ and are very
curious and can't stand it.
Tom Barr

Aquarium Landscapes, ADA & Potassium

by "Roger S. Miller" <rgrmill/>
Date: Sat, 6 May 2000

On Sat, 6 May 2000, James Purchase wrote (quoting yours truly):
> > We've been hearing for years now that potassium can be dosed freely
> > without problems.  That has always seemed to me like advise that had to
> > break down as potassium concentrations became extreme.  I'm glad to see
> > someone finally reporting that problems do appear at high concentrations.
> Don't be too quick to worry about elevated K levels Roger. I've been dosing
> Potassium supplements in several of my tanks at various doseage levels (one
> in excess of 60 ppm) for well over a year, without any problems which could
> even remotely be attributed to an excess of Potassium.

I read recently that hydroponics solutions normally contain a whopping 200
ppm potassium.  The problem with potassium, I think (as with Mg and Ca)
isn't so much the actual concentration as the balance between potassium,
magnesium and calcium.  That is, a high potassium concentration is ok, but
it needs to be accompanied by proportional amounts of magnesium and

Roger Miller

Potassium carbonate/bicarbonate

by "Jamie Johnson" <jjohnson/>
Date: Mon, 12 Jun 2000

With our recent discussions of K+, I thought I'd include a little 
technical summary of the two:

KCHO3 - 39% [K+], 61% [HCO3-], solubility of 35.7g/100ml H20, 
pH = 8.2, derivred by passing CO2 into a solution of potassium 
carbonate in water.

K2CO3 - 56.6% [K+], 43.4% [CO3--], very soluble in water, pH = 
11.6, strongly alkaline, caution should be used.

So, I agree with Roger that the Bicarb of Potassium would be a lot 
safer and easier to work with. And also, Wayne asked about using 
CO2 to make bicarb from the carbonate solution and it looks like it 
can be done. Good luck Wayne and let us know how it goes.

Jamie    <"\\\><

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