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Re Iron

I have chopped up Tom Barr's post solely to make a few comments shown
in [[[brackets]]].  Tom's post replies to some of my previous remarks
marked with the > character.

> (3) if you add lots of iron, then the plants will Look (grow?) even
> better than if you didn't add the iron.

Sure it's the iron? Trace mixes have other things in there.

[[[This wasn't meant to detract from the value of traces.  Merely
regarding iron, I thought I understood you to say this.  Instead of
"lots," maybe I should have said 0.5-0.5 ppm. ]]]]]
> (3a)-- This might be so despite (1), perhaps because what plants
> need and what they can use is very different.  In other words plants
> can benefit form more than they need OR

What's "need"? To stay alive or to be optimally healthy or?

[[[[    I was trying to reconcile so many people getting by with levels
of 0.1 ppm and your suggestion of 0.5 - 0.7 ppm.  I was aiming at
something like, they grow and don't look sick at a much lower levels
but look even better at the higher levels. ]]]]]]

> And lastly, we have the Barr Conjecture, that
> (5) Adding lots (0.5, 0.7, 1.0 ppm) of (total?) iron doesn't (or
> needn't) encourage long term increased presence of algae.

Well it may be conjecture for you and others but it's not for me. I've
doping the tank that high for years. Claus had recommended it to most
tank he saw in SF.

[[[[By "conjecture" I did not mean to dispute your view nor diminish
it's importance.  I meant "conjecture" only in the strict sense, which
I thought you yourself indicated, that you haven't proven how this
works, but loads of anecdotal (in the strict sense) data. ]]]]]
> I don't know if (5) is generally agreed upon, but does anyone have
> counterexamples to compare with Tom's examples?

I can give you some examples but they mean nothing if you have poor
ranges on the other levels. Low CO2 levels will cause problems.
Low non existent NO3 levels low K and no P etc. You can do a low P/high
NO3 tank very well and many do. But it seems to slow plant growth. If
you look at the plant physiology further and what the P does in 
sugar/starch(antiport system on chloroplast) usage and many other
functions you'll see it is very important to plant growth rate and it's
"food". From what I've seen the P is very important. Balance is often
what's referred to. So if you "limit" something down far enough because
your scared of algae, you risk the same problem, this gets away from
the idea of balance. Not good IMO.

[[[[Isn't it one of the thornier problems, that so many factors are
involved that it's hard in any one case to point to one thing and say,
for example, "it's the iron" or "it's the CO2?"  I think it's a key
reason that folks look for guides rules, and formulas. ]]]]]

Iron is a testy ball of wax. I'm not certain if I am truly
limiting/balancing it or not. That bugs me somewhat(on another level
than simply trying to grow plants).

[[[[It's this sort of genuine curiosity that tends to bring the current
state of knowledge forward.  It's good to know someone is bugged -- and
I mean that in a nice way. :-) ]]]]

Thanks for the comments,
Scott H.

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