Well,

Once you start adding ppms to things and causes, you'd better know and be pretty careful how you say it. I was very leary about using specific ideal ppms for planted tanks when I started out with the Article:

A List of Levels and Parameters:

References

So I used ranges which are better than single points.
I conferred with Steve and other folks for sometime before hand and we came to a consensus based mainly on the plant's responses to nutrients/CO2/light.

This was 10 years ago.

Back to the issue: one case is no scientitfic law, it needs to be checked and double checked. Others need to check it and make sure.

I fully tell folks the ranges I test and measure so that they might be able to use this as a reference and hopefully will test and modify/reject my theories in the future or further confirm them.

It(Mg excess) seems to be very low IME/IMO to cause stunting(only 10ppm? that's suspect which is why I tested it!), alkalinity is another matter(and has a much higher ppm range before things happen also) with some species, but these are more general for all nutrients when that is added with some of the Rotala species.

I think if you have 15-20ppm of Ca, ansd 10-12 ppm of Mg, that's fine.

Think about it this way: how much do you have to have before it becomes limiting? 0-1ppm Ca++ or so.
How much NO3 can be used in a week?
Likely more than Ca++.

You can always add some CaSO4/CaCl2 also.

Speculations get multiplied rapidly.
Another similar case was that high K+ causes stunting, that was all the rage about 2-3 years ago by a select few, a few bandwagoning, even though folks had no issues with it for a decade prior. That observation was gleefully tossed out the window

I pointed out this but brick wall thinking would not listen.
"Tom Barr does not know what he's talking about".

Finally, setting up the experiment again to show it did not occur, I showed I had no such effect. Same with Erik's 100ppm + tank that won best of show in the AGA event in 2001. No peeps from the peanut gallery since.

Now for that to be accepted as a true theory, why did it only pop up in this select few folks, why right then and why where they so ready to suspend all logic and past work based on a misapplied belief?

I gave them examples to try out.
Not one of them ever did a single test.

Today, do we hear about such poppycock and K+?
No.....but you have to wonder why not........

One example of induction is hardly a precedent for a theory, nor a validation of any hypothesis.

I think the idea of induction is a huge problem with the production of myths in this hobby. I am very agressive towards these for that reason.
It's not because, I'm like some, butt head and enjoy messing with people.

PPS was founded on induction rather than deduction experimentation like PMDD and the Sears Conlin article.

My notion grew out of PMDD and envolved into a simpler version: EI.
I really did not modify PMDD much, just add a bit more and added more PO4.
Paul had never said no PO4, just low PO4 was required.
I saw things differently and was able to show it for that issue.
So the theory was rejected as to "why", but the how essentially remained fairly well entrenched and is still today.

Why would an aquatic plant stunt due to higher than 10 ppm of Mg?
That's an interesting question, so I set out to see if I could see the same thing. While I did not find the same impact as Edward, I can at least say what Mg 's effect is not at a given amount, he still cannot say with certainly what did cause his stunting(a much harder question), although he may want to believe it.

Thus ruling all possible variations of the hypothesis is a slow method, but a much more careful one.

I get lucky every so often and find a good cause after trying almost everything else. Lots of work though.


Regards,
Tom Barr