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RE: Kitty Litter & CEC

>THe very fine particles that you mention are the "good guys".  The main
>reason to use the kitty litter is for the increased CEC compared to
>regualar gravel.  Sooo, if you remove a large portion of the fine
>materials you have greatly reduced the CEC and thus the effectiveness of
>the  substrate, it you are using the kitty litter for CEC.

Ahhh, the nub of the issue. CEC. I read a post on this list almost every day
extolling the value of a high CEC in a substrate. I've done my research and
see that in terrestrial agricultural books they also like high CEC values to
grow food crops.

I understand the theory, but the practice is something else again. We are
not growing corn in the back 40. We are growing aquatic plants in small
glass boxes. I know that many aquatic plants grow in muddy substrates in
nature, but in nature the volume of water and the rate at which current flow
changes the water around a plant is many, many orders of magnitude higher
than what we have in our aquariums.

Might we be either carrying the importance of CEC a bit too far, or might we
be ignoring the environmental constraints of small glass boxes full of
"stagnant" water (stagnant as compared to natural conditions)?

Plain quartz gravel has no CEC to speak of. Laterite probably has a CEC of
4. Yet the combination of plain quartz gravel over a layer of laterite works
very well to grow aquatic plants in an aquarium.

Flourite is composed entirely of medium sized particles - there are no
"fines" left after you rinse it prior to use. I don't know the CEC of the
stuff, but I would venture a guess that it is much less than kitty litter
due to the facts that it is fired and composed of medium sized particles
rather than finely divided ones. But it certainly can grow nice aquarium

In addition, both laterite and flourite tanks avoid one of (what I perceive)
a major drawback to kitty litter - fouling of the water column when
uprooting plants.

It would seem to me that while a measure of CEC might be important for our
purposes, it doesn't seem to be necessary to go to extraordinary lengths to
see it top 100. If it was necessary, please explain the success of the Dupla
style substrate?

Could one of the aquatic botanists or perhaps a chemist on the list add
something to this, please? Are the high CEC advocates missing something? Is
there a danger from drawing parallels from growing food crops on land with
growing aquatic plants in aquaria? I mean, a substrate has a number of
purposes in an aquarium, and being finely divided muck doesn't seem to me to
be such a good idea.

Enquiring minds want to know. At least one inquiring mind wants to know <g>.

James Purchase