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Re: Iron

> Again this points to one end of the spectrum of choices.  If I am
> reading Tom's and Roger S.'s posts right, the following is generally
> agreed:
 
> (1) plants need very very little (available?) iron and if the substrate
> has iron (flourite, laterite, iron tablets), then the plants (or only
> the substrate-rooted plants) will get enough.

2 part question. What's "very little"? and perhaps yes tot he 2nd.

> (2) you must add lots of (chelated) iron to the water column to make a
> little of it available to plants.

I suspect that the iron is available but for only a very short time window.
At higher levels(say 1.0ppm) the plants have enough time to get this rich
level than at lower levels. I suspect that is why the high levels show a
better growth even though shortly there's less bio available left after
additions.
Maybe........I'm not sure, just a "perhaps" there. Seems plausible.
FWIW, some plants will pull in Fe and then chelate it themselves for
transport within the plant itself.

> (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.
 
> (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?

> (3b)-- This might be so because of (2), in other words, adding up
> to 0.5, 0.7, or even 1.0 ppm (total iron?) levels gets the iron that's
> most readily available to the plants up to the required level OR BOTH
> 
>(3c)-- This is only so in high growth setups, added CO2, macros,
> and other traces.

I add these levels only in CO2 tanks. Non CO2 tanks get none.

> (4) Walstad's observations, seem to me to be consistent with (1) - (3).

This is a radically different approach than a CO2 tank. Only a few folks on
these list even do this approach. Few are patient enough and reap the
rewards. I wish more would try it that complain about all the maintenance.
Feed fish and prune once in a while. Not too bad I think. Most folks got to
mess with the stew though. They cannot just let it simmer.
> 
> 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 been
doping the tank that high for years. Claus had recommended it to most every
tank he saw in SF.
> 
> I don't know if (5) is generally agreed upon, but does anyone have any
> 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.

Both the N and the P methods of nutrient management are easy enough to test
for. 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).

> My own example that
> started this round of posts fails as a counter example, at a minimum,
> because I didn't "power through" until the algae growth rate subsided.

Well once you've gotten everything set up and with good kits you can tell us
yourself:-) If you hit the level ranges I mention you will have the same
results. That's an "IF".
It's(these ranges) more flexible than many think it is. Got to work on the
light/CO2 first then move on down the line to the macro's them finally start
in on the traces.

If you have problems with the CO2, or the macro's your going to have
problems assessing the traces. Work on those first and worry more about them
more than the traces. Come back to the traces after your confident of the
other 3 things(light,CO2 and macro's).

regards, 
Tom Barr