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Re: Substrate iron

Steve writes:

<snip>> Diana Walstad pointed out that if all of the iron in a soil
>  substrate could be made available to the plants, it would be enough to
>  last thousands of years.
>  My understanding of the processes suggests that there are two dominant
>  factors:
>  1) chemical availability which really means that the soil particles are
>  very fine in texture such as iron oxide or hydroxide clay. Refer to the
>  links on my web page on soil science and the recently mentioned link
>  "Plant Nutrition Lecture List" for discussion of iron availability in
>  latersol and oxysol soils.
>  2) the presence of small particles of stable organic matter such as
>  peat. These peat particles maintain reducing environments
>  (micro-environments as described by Roger Miller in a previous email
>  several months back) which solubalize iron and provide a source of
>  organic Fe complexes which help solubalized iron be transported by
>  diffusion to root hairs. Only a very small amount of peat or other
>  stable organic material is necessary.<snip>>

So if I use redart at a 200 mesh (about like flour), with its 7+% Fe2O3, and
add peat into the substrate, I should be able to get a very long term iron
dosing, possibly even too much at first.  When the initial humus and tannins
wear out, will the peat continue to function as a reduction "catalyst"?
>  I've found that initially these soil/clay substrates provide a large
>  amount of iron and with significant amounts of peat, the humic acids
>  released into the aquarium water actually provide more iron in solution
>  than I want. During this initial transition phase, I think it's
>  important to make frequent water changes or to provide regular carbon
>  filtration (with weekly replacements of the carbon media) in order to
>  - -reduce- the amount of soluble iron in the water so as not to encourage
>  algae growth. I don't think it actually makes very much difference how
>  much substrate there is; Paul K has used soil substrates of 1/2" depth
>  for long periods. I recall that he observed that when he mixed peat with
>  the soil in these soil trays, that he never observed the plants to
>  develop iron deficiency. Presumably the peat prevents a condition where
>  the soil becomes so oxygenated by the plant roots that it no longer
>  provides sufficient reducing environments to solubalize iron.
>  <Snip>>
As long as we're talking about the benefits of peat,. has anyone out there
used the Amano  "Substrate Gold", which is primarily pumice and peat?  Any
estimate about the percentage of this substrate that is actually peat, volume-
wise?  Weight percentages would probably be a tougher call with pumice being
so light.  And is it peat in pettet form like the Fluval, or a more natural
loose peat?

Bob Dixon