Re: vermiculite, laterite and $$$

>From: George Booth <booth at hpmtlgb1_lvld.hp.com>
>Date: Wed, 30 Aug 1995 10:00:06 -0600
>Subject: Re: nutrient diffusion into substrate.

>If you used a layer of pure laterite, I have no doubt it would form a
>dense compacted mass.  But in the aquarium, a small amount of laterite
>is mixed with a large amount of gravel.  The gravel will not compact,
>unlike the mashed-up vermiculite promoted by others.  The gravel
>itself will provide the intrinsic, well-areated macro form that is so
                                    ^^^^^^^^^^^^                 ^^^^^
>desired while the small amount of laterite scattered around the gravel

>voids will provide all the CEC necesary for excellent plant growth. 

It is only desired if all of the nutrients enter the system thru the water,
if the iron is chelated (so no reduction of Fe+3 to Fe+2 is needed in the
substrate), and if the amount of plant growth is limited.

I have several very successful plant tanks which derive many of their
nutrients thru the reduction processes that occur in an oxygen limited
substrate. These tanks have a soil or clay enriched substrate without
artificial circulation and utilize 'natural' circulation by diffusion and O2
injection from the plants. 

Circulation thru the gravel may be desireable, but it is definitely NOT
required. At least for the
experienced aquatic gardener <g>. But, I am curious enough to want to try
artificial circulation
some day. I even have the cables and a transformer and some 7w heaters for
the Randall system. I
just need the time to set up the tanks.

>After all, if vermiculite were so desireable, why would not Dupla
>package it instead of laterite?  Surely, it would be cheaper to
>package and would provide even higher profits than laterite. 

But then, would there be a market for their heating coils? <VBG>. 

>What you seem to be saying (and I exaggerate here for effect) is that
>there is something wonderful about vermiculite that ....

BTW, I tried vermiculite not as a sponge to soak up nutrients, but as a
substrate "conditioner,"
just like it is used in house plants - to open up the soil and keep it from
compacting.  I mixed
the vermiculite with sand and peat in the lower half and used clean sand in
the upper half. I wanted to create an O2 deficient environment. The
vermiculite/soil tank is getting torn down this weekend.
Maybe I will try artificial circulation!