Re: Substrate query

Miles Morrissey has substrate questions,
> I was thinking of using vermiculite, top soil and 500g of 
> duplarit. Is this over kill? 

a difficult question but if you're not concerned about expense,
the addition of duplarit will probably improve the substrate
possibly by enriching it with aluminum and iron oxides and silicates.
Top soil contains iron already but perhaps not in as high a
concentration as laterite. A low cost alternative might be to
enrich the lower layer of substrate with iron oxide.

> The duplarit suggests mixing it with the 
> first inch of gravel, should I add some gravel to this mixture to in 
> order to resist it getting too compacted?  

If the laterite or iron rich clay is in the bottom layer of a
substrate, I wouldn't be concerned about it becoming compacted.
You don't really intend for the roots to extend far into this
zone; it would be a reducing zone designed to reduce Fe to Fe++,
it's (more) soluble state. I would use straight clay for the bottom

To prevent compaction of the middle, nutrient layer, you should
use the vermiculite. It's flake structure greatly reduces the
density and allows easy penetration of roots and diffusion of
nutrients through the interstitial water.

Don't know about Ammano's methods.

> Lastly, I'm going to use Malaysian trumpet snails but I've 
> heard that this is counter indicated with soil substrates as their 
> burrowing will disturb the soil causing it to disperse into the water.  

I don't believe this is a problem but let's see if anyone else can
relate experiences. My Malaysian trumpet snails were only recently
introduced and probably have not propagated much yet.

> How about a nylon screen between the soil and gravel?

I wouldn't. Roots would grow into it and you could have a
terrible mess if you tried to pull up on even a tiny plant.
You couldn't extricate the plant intact. An alternative to
aquarium gravel is a nice clean sand (washed) such as white
silica sand. I suggest washing it yourself to remove any dust
even if its already washed. (from experience)

To review, I suggest a dense lower clay layer enriched with Fe
oxide; a middle layer containing cleaned soil (see P Krombholz
soil soup method) and peat or vermiculite; a top layer of
clean sand. You could also add s-l-o-w dissolving fertilizer
bits in the lower-middle level as suggested by Jim Kelly.
Another option is to put the fertilizer into DIYS clay balls
as recently suggested in another post.

Steve in Vancouver BC, blue skies, sunshine, low 20s C