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[APD] RE: testing for K+

> "If I have 50ppm of K+ and excessively high iron content in my water, 
> does K+ block Ca++?"

>*"excessively high iron content in my water"*, 
That is NO quote of mine.
> You're assuming a linear model without considering possible correlations 

No, not really.
Either it(high K+ at 20ppm or higher) causes poor stunted plant growth or
it doesn't.
 I never said anything about iron. I also did not say _what_ it was. I
simply said what it is _not_.
I did answer the question as to whether high K+ caused Ca++ blocking and
stunting characters in Ammannia gracilus. 

There might be Si, Fe, NO3, or some organic thing, who knows..........
I do know I've done this with several tap water types over a long time, the
likely hood of these multiple correlations starts to go way way way down
when you run the test again and again over long time peroids and under many
different tap water and plant species changes.  

It takes a long time to figure it out and you get a good feel for what it
likely is, we may never have precise knowledge about everything, but we can
make some arguements based on what we do know and what we know it is not.
Even then you may end up stumped after a decade.......... 

> - the real world is nasty and non-linear and correlated.  It might be 
> excessive K+ in the presence of high silicates blocks Ca++ uptake. 

I merely said what it is NOT, rather than what it is. 
I can spread doubt and unkowns to many things.............even things that
are seemingly very obvious(like light and CO2).
I did not test nor design my test for multiple interactions. Someone said
high K+(20ppm or higher) causes Ca++ blocking uptake. 
My test answered that question, it did not answer why some folks had issues
with some plant species. 

The test needs to answer the question you have. 

I did not ask why they had problems when they throttled the K+ up and down.
I did not feel I could answer that issue since I have no control over their
tanks nor know what other things they might be doing to it.

It's not K+ like I said to begin with, it's multiple interactions(as you
have suggested, perhaps...) and not an isolated situation.
I never said this was linear or not. I think in graphical terms when I
think about uptake and blocking. Logs, non linear, correlations vs
causation, manova/anova, happy stats. Few things in biology are linear.

The doubt is on these folks running these "test" when they say K+ blocks
I proved that incorrect. If they want to say that it's K+ high and also low
Traces andf low NO3, then that is another different question.

I did NOT prove that there were no multiple interactions or that NO3 does
not cause the same effect if it's very low(But it will if you'd like to try
it) on the particular plant species of interest.

We need to be plant specific as well here. 
Many of their plants did not have that stunting...........
Some did.........

I do not get the same results they claim for these reasons, nor have for
many years under and wide variety of real world  conditions and lab
Nor do other folks I know that have also run decent controlled K+ test.
I cannot repeat the K+ effect, nor can they. So this really show a huge
degree of doubt that it's K+ causing this. 
I have complete control over my parameters, so I can manipulate one at a
time or two etc.
Most hobbyists do NOT have this type of control and those that do, seldom
are willing to torture their tank after they worked hard to get it there. 
I've spent a lot of time torturing plants and trashing my tanks rather than
aquascaping. I destroy the tank, then re work it and start over.  
I've never really said why they have these problems. I've speculated and
suggested what I might do to try and address things.   

> excess K+ without sufficient iron causes problems, etc, etc, etc...

Well then the K+ was never isolated as the dependent variable.
So if you want to discuss oranges when we are talking about apples.....

They asked about K+ causing Ca++(no other varibles), I say when monkey's
fly out of my butt.................

You cannot have any conclusive arguements without addressing the
independent variables like Fe, CO2, lighting, NO3, etc. 
Until the aquarist can master those variables, they will not be able to do
these types of experiments to find out. Then they need to be willing to
trash and torture the tank to answer their question. Few will ever do this.
I am a "Curious George". Not G. Booth, the monkey. 

> real close to shelling out some good money for an experimental setup 
> where I can toy with these things a little more, I need to move some 
> furniture in the basement around and come up with a cheap controllable 
> CO2 injection system for smaller tanks (~2 gallons).

Try 10 gal tanks, they are cheap and allow a bit more room and less
You do not have to fill them all the way either.
I've been testing and torturing tanks for over 15+ years now since I got
that pesky 100 gal maximus filter project tank.
I've set up bare tanks, planted, fish loading, NH$, no herbivores, all
sorts of nutrient combinations etc.  

> But I have read from more than one person that they have done K+ on, K+ 
> off, K+ on, K+ off, and have seen stunt, no stunt, stunt, no stunt. 

I've read it as well.
We never saw that till recently though.........so that's another
observation we should look at. The other issue..........which plants are
All species? Some species? Which species?
They said Ammannia, Nesaea, I don't recall other plants, but both of these
plants both Erik and myself have grown like weeds at high K+ levels. 

So if the high K+ issue is an issue, it has more than one variable(like Fe
or Ca or NO3-my personal fav or PO4 etc).
One variable issues are relatively easy to address, combinations require
more work, but I was heading this direction anyway with Barr's laboratory
2x and then after I've done enough of those, 3x.

I am not pursuing the traces as much, I'm mainly going after K, Ca, Mg,
PO4, NO3, NH4, CO2 and light. 
These will play the larger roles I'll assume. Traces tend to be tough to
observe their effect on growth and take longer to see differences. I simply
will never have enough time to test for the rest of the possible
cominations and dont have the time nor energy to pick apart very subtle
So I make guesses at what ones might have the greatest impact.

Damn stuff either works or it doesn't.
If adding high K+ causes a problem, don't add high K+.
See what I'm adding, see what others that do NOT have the problem are
adding, do what they do.

The actual question "why" is another matter. 
Most are happy with "how" and then can think about "why" later. 

> warrants some more detailed study and we need to tease out what the 
> correlating factors are, I think they might be out there...

You need to find out what the folks' that had the issues to begin with, did.
The signs based on the plants seems to point to low traces/NO3 to me
The plant issues were species specific, and I've had these same species do
the same thing with NO3 issues.
Many have NOT had any K+ issues with these same plants under non limiting
These are important observations and in many ways, more important. 

> Jeff Ludwig
> Elkton, MD
> http://www.rockytop.net

Tom Barr

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