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Re: Steel Wool for a source of iron?
jlemons at myriad_net wrote:
> I have seen several people meantion that they put steel wool in their substrate
> as a souce of FE. I was wondering:
> 1) what are the effects of excess FE in the water column
Free Fe cannot exist in more than extremely small concentrations in the
water IF there is free oxygen present unless the iron is chelated. Iron
can be chelated by the commercial chemicals such as EDTA or DTPA (or
others) or more weakly by humic acids such as those released by peat.
Put another way, iron or iron oxide won't dissolve in water however
complex molecules containing iron together with carbon, hydrogen and
other atoms can dissolve.
Excess chelated iron will result in growth of various kinds of algae.
Very high levels of iron might be toxic to fish.
High levels of iron (and other compounds) in the substrate can harm the
roots of the plants unless the plants have adequate supplies of light
and nutrients so that they can produce oxygen which they bring into
their roots via air channels called aerenchyma.
> 2) could it be places in one of the baskets of my Fluval 303 or in the media
> basket of my Emperor 400
No. In order for iron to become available to plants, it must either be
present in chelated form, or in reduced form in the substrate. Reduced
form means that the iron ion has accepted an extra electron to form
Fe++, the ferrous ion which is slightly more soluble than the oxidized
form Fe+++, the ferric ion. Plants get at this substrate iron by sending
our microscopic root hairs from the visible roots.
> 3) How much would you reccomend for a 70 gal heavilly planted tank
You need to maximize the surface area of the iron materials so fine clay
is the best. Limestone clays do not contain much iron however these
types of clay will produce an alkaline reaction when tested for pH. Red
clays very often contain significant amounts of iron as do soils in
general. If you have a soil or clay which is suitable for growing
plants, then it probably has enough iron for the purposes of an
aquarium. If you have an iron rich clay, you probably only need a couple
of pounds if you mix it well with a sandy material such as subsoil. In
fact most subsoils already contain a mixture of sand, silt and clay
where the sand particles are coated with very fine clay particles which
maximizes the surface area of the clay and the availability of the
micronutrients to plant roots. It should rarely be necessary to
supplement a clay with iron but if you wish to do so, you could add a
few handfuls of a product called Micronized Iron. Again, this should be
well mixed with the sandy silt (sometimes called loam).
It is important not to use an excessively deep layer of top soil (if
used at all) since this contains organic materials which consume oxygen.
If organic materials exist much below 2" in the substrate, oxygen does
not penetrate to these depths and so the reducing action of bacteria
below this depth can be too strong. You don't really need to use an
organic soil at all however I sometimes use a little bit in a thin layer
because it contains macro nutrients which really boosts plant growth.
I'm not sure that even super fine steel wool will have enough surface
area to provide a good source of iron for plant roots. Instead, its
probably more economical and effective to use clay or clay supplemented
with a few handfuls of micronized iron and mixed very well. Clay
particles are microns in size whereas steel wool is thousands of times
My feeling is that you wouldn't need more than a kilogram or two of clay
if you mixed it well with sand or subsoil. In this way, it can be used
very much like laterite and mixed into the bottom layer of the
> 4) whats a good FE test kit so if I decide to do this, I can both quantitativly
> and qualitativly report the results
With iron in the substrate its unnecessary to add chelated iron to your
water. If you have used peat in your substrate, the humins released may
carry iron into the water and this may cause you algae problems for the
first few months. A test kit might be useful to see how much iron you
are getting in solution. I think that most test kits have no problem
reacting with iron which is weakly chelated by humins. For the
commercial chelating agents such as EDTA or DTPA, you need to allow the
test sample to react for several hours to break the strong chelation
bonds in order to form the correct colour. If you have yellow water from
a new substrate, it would be advisable to apply activated carbon
filtration to reduce the amount of iron available in solution. Remember,
the rooted plants have access to the iron in the substrate.
> 5) any potential downfalls that I'm not taking into consideration?
Ensure good lighting, dense planting and adequate nutrients including
CO2 so that the plants are actively growing. If you have used topsoil or
organic materials such as peat, these tend to use oxygen, and you want
to keep a healthy balance by having lots of plants producing oxygen.
If you use any topsoil at all, I think it should be mixed with sand. You
really don't need to overdo the fertility. I would not use any
commercial potting soils or garden soils because these tend to be quite
fertile or high in peat content. There are a few commercial tops soils
which are purely mineral but I think you are safer with subsoil or soil
which you find yourself. Its much easier to find a well leached safe
soil by taking a little walk with a pail and shovel.
You can find a lot more information about substrate iron on my website
substrate article at http://home.infinet.net/teban/substrat.htm#Iron
You can also find directions for preparing safe and productive soil
substrates at http://home.infinet.net/teban/how-to.html
There might be an application for iron in a filter if it were effective
at removing dissolved phosphates from the water. Iron and phosphates
form an insoluble precipitate. Some scientists have experimented at
using soluble iron salts (iron sulfide or iron chloride) to reduce
phosphates in an aquarium however the results and conclusions were
controversial. There was an article in TAG about that. I think it
-might- be risky to try in a home aquarium but it would make an
interesting experiment if somebody wanted to try it on a limited scale.
At the worst, you could get a lot of green thread or black brush algae.
At the least you would probably get a lot of hard black spot algae on
the glass and leaves depending upon how much iron you were able to get
into solution. If you overdosed the tank with iron sulfide, you might
even kill the fish. I'm not sure what the chemical reactions would be.
If all you did was add steel wool to your filter, I doubt that much
would dissolve at all. Has anybody ever put steel wool into a filter?
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!!!