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Re: Shelf life of Flourish/Substrate iron

Justin Collins writes:
> This has not been my experience.  I use a 50/50 mix of relatively fine gravel and
> Seachem's Fluorite substrate which (they say) has iron in it.  I have found that
> if I do not dose with supplemental iron the leaves of my normally red-growing
> plants start growing green.  I dose with iron, they turn red again.  Now, this may
> be because the plants have a hard time getting at the iron in the substrate, but
> I'm not sure they aren't using all the iron available to them, as I have 260 watts
> over a 60 gallon and fairly high CO2 levels.  Is it possible I simply have more
> photosynthetic processes that use more iron than in some other tanks?

Fluorite may or may not be capable of satisfying all the iron and micro
nutrient requirements. Isn't it rather coarse in texture in comparison
to clay? The texture of the iron bearing material is critical to
providing sufficient surface area for it to be sufficiently available.
This is why iron enrichments like Micronized Iron are provided in fine
powdery form.

This is another example of confusion over the symptoms of iron
deficiency. The red coloration of plant leaves is unrelated to iron
availability according to reliable information by Diana Walstad in TAG.
Red pigmentation is a protective response of plants to intense light
which provides protection from UV radiation. It can be stimulated by
intense lighting and possibly by the use of strong actinic lighting. In
fact, I'm pretty certain that Justin's plants take on a red color of the
leaves as the stem plants grow closer to the surface and get stronger
light.

Let me clarify slightly what I said previously; an experienced aquatic
gardener is probably able to determine from experience and very careful
observation, the symptoms associated with insufficient chelated iron. A
severe shortage of Fe results in chlorotic coloration; leaves with
yellow areas around the veins. Unfortunately, many other nutrient
deficiencies are quite similar in appearance. A shortage of nitrogen for
instance, also causes chlorotic leaves. Before chlorotic symptoms set
in, a reduction in growth rates might also be observable. Its not easy
to tell what nutrient is in short supply unless you add them one at a
time over a period of a few weeks and carefully watch for changes. It's
just as easy to be mislead by other factors such as the establishement
of roots and other physiological changes in the plants themselves.

One safe way to provide iron is by using a soil containing iron bearing
clay. Clay particles are extremely fine and provide the high surface
area required to make iron available. It is not necessary or
advantageous to use large amounts of clay; a pound or so mixed with
silt, sand or gravel would suffice. Ordinary loamy soils frequently
contain sufficient ratios of clay, silt, sand and humus.

Another excellent way to provide iron and other micro nutrients for
plants is to use a calculated daily, or weekly dosage designed to
maintain a -low- level. Please refer to the PMDD articles, The Optimum
Aquarium book, George B's website or information on the use of Tropica
Master Grow provided by Karen Randall for more on dosing micronutrients
in solution. 

You probably are fine with concentrations of much lower than 0.1 ppm
however this is close to the lowest resolution that commonly available
Fe test kits can register. I have strong suspicions that some test kits
simply are not accurate either.

I would like to see someone make a calibration test of several Fe test
kits using precisely weighed amounts of chelated Fe in distilled water.
Several people can participate in this study; in fact, the more people
involved, the better. For people here in Vancouver with iron test kits,
I can prepare standard test solutions using the chelated trace element
mixture which we have available and is used in our PMDD.

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!