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Re: Silica and making your own laterite

Bill gave some info on silica:

"I would say no, since Silica that we see in fish tanks is silicon dioxide
(SiO2) I believe, this form is highly insoluble in regular water. I think
though, that if you want to worry about more soluble forms of Silicon in an
aquarium, you should look at your precious laterite, yes, all clays are made
up of a large percentage of silicon Dioxide. Those of you familiar with
(my father is a potter) will know that Kaolin is nearly pure Silicon
and that the percentage drops as you come closer to laterites. Though even
laterites contain a large percentage of Silicon. Though silicon is highly
insoluble, even in that small a size, the energy taken to break those bonds
or Oxygen and Silicon is very high, it takes a very hot fire to make the
silicon bond with anything (i.e. porcelain)."

I doubt that much silica would dissolve out of sand, or that the glass in
our tanks is leaching silica into our tanks (at least not at a rate that we
need be worried about). SOME clays do contain silicon in a form which can be
dissolved in water (PyroClay is one that I know of, see

From everything that I have ever found out about the formation of
"laterite", it requires that the source material be "weathered" over
geological time, i.e. thousands or tens of thousands of years, under
tropical conditions (i.e. very moist at times). To my mind at least, this
would seem to indicate that anything in the source material which _could_
leach out easily, _would_  have leached out, and would have done it long
before someone came along and dug it up and used it in an aquarium. I may be
worng, but it seems only logical.

"On another note, I've discovered that when we're talking about the
different types of clay, Red clays have iron, yes, but they also have lots
organics involved, which raises their CEC content. I am starting to get the
idea, that Laterites could be easily reproduced simply by adding organics
some cheap chelated iron supplements to them."

Don't confuse laterite with red clay. Some laterites DO have a bit of
organic material in them (I think that Duplarit G was shown a few years ago
to have a percentage of organic material) but others, like Karl Schoeler's
Substrate Gold was described in the same study as having no organic
material. Check with the archives for those discussions.

I think that it might be a bit ambitous to think that you can reproduce
something (cheaply, anyway) which has taken millenia to form by mixing up
some pottery clay, iron filings and peat moss. Of course, that's not to say
that those three things can't be used productively in a substrate mix.

"Those of you who dislike
commercial intrusion into our hobby, I think we should re-examine the idea
"magic clay"."

Without commercial involvement, our hobby would not be where it is today.
Some commercial companies conduct very valuable applied research based upon
sound scientific principles and base their products on that reasearch. We
all benefit from the work of companies like that.

James Purchase