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pumice and the CEC of peat

Bob Dixon <IDMiamiBob at aol_com> writes:
> >From what I have read on this list, I have gained the understanding that peat
> has a really lowsy LOW CEC.  Have I gotten confused in trying to acquire
> knowledge here, or are they in conflict with the generally accepted theories
> of the experienced aquatic plant folks on this list?

I've been doing a little research on the cation exchange capacity (CEC)
of peat and other things. I came across an interesting web site:
http://peatmoss.com/index.html The Canadian Sphagnum Peat Moss
Association Homepage. I discovered that peat has a CEC of 100-150
meq/100 grams which is very good. Sometimes "generally accepted
theories" need to be revised! I was able to discover several interesting
web sites about soil science and I have updated my web page substrate
article. For one thing, many agricultural soils have a relatively low
CEC less than 5 meq/100 grams. CEC is important for farming soil in
order to prevent soluble nutrients from being leached away into the

> Also: The primary ingredient of this Power Sand substrate is Pumice gravel.
> In my experience pumice tends to buffer pH upward...

This really depends upon the type of pumice however I strongly suspect
that the type of pumice being used in gardening is primarily silica. It
is used in gardening for its lightness to promote aeration in heavier
clay soils. Cactus soil preparations tend to use pumice. I don't think
that silica pumice will have much effect on pH but it depends upon what
other minerals are present. One possibility is calcite (CaCO3). I don't
see much advantage in using pumice in an aquarium except that it might
improve the permeability of the substrate.

See also the web page for Hess Pumice at:
http://www.magicexport.com/pumice.htm and

I have been revising my substrate web article recently and am still
doing updates whenever I find new information. Is anyone using kelp or
seaweed derivatives in planted aquariums?

Steve Pushak                          teban at powersonic_bc.anti-spam.ca 

Visit "Steve's Aquatic Page"            http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!

Aquatic Gardeners Association     -                  technical advisor