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Re: soil instead of laterite
>From: Steve Pushak <teban at powersonic_bc.ca>
>I discourage people from using any commercially packaged horticultural
>soil as these are too labile and fertile to be used in large amounts.
>Pottery clay, subsoil or garden dirt are better choices. Please read my
>web pages if you are interested. Also checkout Paul Krombholz's soil
>soup method in the Krib and APD archives.
>
>Experimentation with soils without knowing what you're doing is an
>recipe for green water but with a little knowledge, I consider it a
>reasonable alternative. YMMV.
Since I use soil in some of my tanks, I think it is time to throw my 2
cents. If anyone is going to use soil instead of laterite, they must
realize that they are taking a chance and as Steve P says YMMV. One should
approach the use of soil slowly and cautiously. A trial use is suggested
before setting up a full blown tank with it. For example using a little in
the bottom of a plastic pot layered between some coarse sand to keep it in
place and then covered with your favorite gravel/sand. I also recommend a
thin layer of filter floss to first cover the holes at the bottom of the
pot. There is also nothing wrong with only using soil in pots or for that
matter, only using pots in your aquarium to grow plants. I have several
tanks whose bottom is completely covered with pots, and they are not
covered over by gravel like (which is Dorothy Reimers method). These potted
tanks are so densely planted that it takes people a few minutes to notice
that the pots are even there.
One must also recognize that when soil is first submerged, it will undergo
changes and release some potentially toxic substances. This can be managed
in several ways, including a complete water change (obviously a nuisance)
and adding a chelator to bind any dissolved heavy metals. This is only a
problem when you are using a lot of soil at one time. Remember: "the
solution to pollution is dilution." In my experience, a handful of sand
covered soil in a 100 gallon tank does not warrant any special treatment.
The subject of soil submergence was thoroughly covered by Diana Walstad and
can be found in several articles in the bag issue of TAG.
Another important point to emphasize is that if you do use soil, you do
_NOT_ need a thick layer. In my experience, the biggest problems I had with
soil in aquaria was when I used a layer more than 0.5-1 cm thick. One can
follow the same proportions and layering that is used for laterite... and
with similar clayey soils... you "can" get very similar results. I say can,
because all soils are different and until they are analyzed and or tried,
you will not know. I don't use a thick layer and don't like a rich
substrate. I am adding soil to act like laterite - to provide an intial
source of iron (until the substrate becomes root bound and over oxegenated)
and to provide a sink for phosphates. Again, the use of soil in pots is an
OK way to go.
I have the luxury of having a nice source of soil in my back yard. Whenever
I need some, I go in the woods and dig some up. I scrape off the top layer
of leaves and surface tree roots and get the material around 6 inches down.
It is a nice loamy soil. I remove the rocks and as much of the organic
material that I can see. i do not worry too much about the other litter. A
few weeks of composting in a shoe box (as suggested by Paul K. will also
help digest any OM that still needs to decompose). If I were to get soil
from a commercial source (which I tried several years ago), I would look
for the cheapest grocery story soil I could find. The cheaper the
better...e.g. $3.00 for a 40 pound bag. The cheap stuff probably does not
contain bark chips or peat moss or other organic amendments. It is best to
peak inside or find a bag with a small hole to check the consistency of the
material. This is hard for me to describe in words. This is where
experience helps. Maybe a soil scientist on the list can give a good
description of loam <g>. Anyway, the advantage of buying a 50 lb bag is
that it gives the city dweller a source of material that can last a while.
But before you use the entire bag at one time, you must set up a trial pot
under water and see how it works for you. I had to try several different
bags before I found one that worked for me. Except for the fun of it, I
might have been wiser and saved money by getting a box of laterite.
--Neil, AGA