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Re: Natural Waters vs Aquariums & Laterite Confusion

Dear List Members,

Numerous post have been made over the past couple of days concerning
nutrient levels in natural waters vs our aquariums, with much emphasis being
placed on the "limiting factor" where a certain minimun concentration of a
particular nutrient is needed for optimum plant growth. I'd like to come out
of hiding once again and stick my foot in, if I may. (Steve, may I borrow
your shoe?)

First of all, I would like to remind everybody that our aquariums bear about
as much resemblance to a "natural" body of water as a manicured English
Garden does to the Brazillian Jungle. In short, not much. An aquarium is a
highly artifical environment and much more limited in scale and scope than
is even the smallest natural body of water.

We look to Nature for guidance and understanding in the management of our
aquariums. There are numerous interconnected nutrient cycles which exist in
natural waters which we attempt to duplicate in our aquaria. Most of these
nutrient cycles are only imperfectly understood by Ecologists (regardless of
the pontification which sometimes takes place here and elsewhere regarding
them) and rarely are we able to establish a complete and self-sustaining
cycle in a small artifical system. Witness the Nitrogen Cycle which in our
aquariums usually ends in the accumulation of Nitrate in the water. The only
"practical" method to rid our artifical systems of this excess is to
regularly change a portion of the water.

When discussing "limiting nutrients" in both natural systems and in our
aquaria, I have yet to see anyone fully discuss the fact that not only is
there a minimum requirement for each nutrient but there is also a maximum
beyond which growth will be just as limited. For each nutrient, we seek to
maintain a concentration which falls within this range, i.e. not too little
nor too much. Blindly adding an ounce of this and ten drops of that just
because of heresay is not only poor science, it is poor husbandry. As many
commercial preparations on the market do not list complete ingredient lists,
quite a few people do not really know what they are putting into their
aquariums. Moderation in all things is a maximum which can be well applied
to the keeping of a beautiful aquarium.

There also seems to still be some confusion concerning laterite and what it
is and how it works. Some concern has recently been expressed that laterite
might dissolve in the presence of humus (organic material) and discolor the
water column. Based upon my own experience (and I admit that I have
conducted no scientific tests on this - it is just an observation based upon
my own tanks) this is not a concern. I have a considerable amount of
Duplarit G mixed with Sera Peat Granules in the bottom of my 120 gallon tank
and the water column has not turned pink once in the year that the tank has
been operational. Nor does the water cloud up excessively when I uproot a
plant or disturb the substrate. The laterite and peat are under at least
four inches of gravel and haven't moved as far as I can tell.

What I can say about this mixture is that certain plants don't seem to like
such a rich substrate while others really seem to thrive in it. Perhaps when
I next re-do the tank I will pay more attention to preplanning my plant
layout and only place the organic material under heavy feeders.

Someone also made the statement that "laterite normally contains a large
amount of aluminium" which can be toxic when present in excess. I don't
doubt that aluminuim can be nasty when there is too much in the substrate
but as far as I can tell, true "laterite" does NOT contain a lot of
aluminium - it has been leached out of the clay by weathering over thousands
of years of exposure to seasonal rains. Many people attempt to save money by
using a form of bauxite clay in the belief that this is also "laterite". It
is close, but doesn't deserve a cigar, as it has not had the opportunity to
have the excess aluminium leached out of it (as has the laterite packaged
and sold by Dupla). I guess its a case of paying 'yer money and taking 'yer
chances. Dupla Duplarit G is relatively expensive but you don't need a lot,
and it DOES work.The cost of plants for a tank is usually a lot more than
the cost of a box of Duplarit.

James Purchase
jpurch at interlog_com