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Re: peat and pumice

Bob Dixon wrote:

> >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 expect peat to have really variable properties.  It can have a high CEC,
or it can have a very low CEC.  Low CEC would probably be the case for
coarse-textured material.  It can buffer pH to very low values, or it can
have little effect at all on pH.

I suspect that if ADA is advertising that theirs has a high CEC and
produces the a good pH then they probably located a source for
fine-textured, high CEC peat and are using it.  But I don't know of any
way to test it, so Buyer Beware.

While I'm thinking about it there may be a way, using an ammonia test kit
and chemicals common around the house of in the hobby.   Hmmm...

Also, the CEC of natural ion exchangers (peat, humus, soil organic matter,
etc) is pH sensitive.  It increases as pH increases.

> Also: The primary ingredient of this Power Sand substrate is Pumice gravel.
> In my experience pumice tends to buffer pH upward, which is inconsistent with
> the goals of folks working with Discus, Apistogrammas, Angels, and other South
> American fish.  Anyone else have experience with pumice in their tanks?

There's some pumice in the river sand I've collected locally, but it isn't
all pumice, or even mostly pumice.  I've always discarded the larger
pebbles and picked out the smaller pebbles if they move around in the
current.  Pumice (at least what I call pumice) floats when its dry and is
very light after it's waterlogged.  What ADA sells probably isn't quite
that light.

I've never noticed a problem with it increasing pH, but my pH is fairly
high anyway.

Roger Miller