Re: Substrate suggestions

Matt wrote:
> I've heard of using "red art clay", vermiculite, peat, and a 
> half dozen other combinations.  What do you use, has it worked for 
> you, and what would you recommend.  I am willing to spend the money 
> for dupla's laterite if it is far superior to any other option.

I've used regular gravel supplemented with laterite like additives
and a soil/vermiculite/gravel composite with a layer of gravel on
top. Both have worked well but I think the later works better. It
seems to provide a better supply of Fe for the plants. Next time I
won't bother with vermiculite; I used it to promote the permeability
of the soil because I was concerned about anaerobic conditions in
the substrate. This is not really a problem; in fact the opposite.
Plant roots provide a large supply of oxygen into the substrate and
the induce a flow of nutrients into the substrate by drawing water
up through their root systems. Probably the best attribute of
vermiculite is that it might help facilitate root penetration by
avoiding compaction of the substrate.

There does not appear to be any conclusive evidence that any one
substrate preparation has vast superiority over any others although
there are obviously certain advantages to some.

Soil has the advantage of providing good CEC, some trace nutrients
including iron (Fe), a reducing environment at the bottom of the
substrate to permit reducing insoluble Fe to a more useful state,
a beneficial environment for soil bacteria, and a fine material
which encourages root hair growth.

It has the disadvantage of producing cloudiness (turbidity) if you
disturb the substrate which may last a day or two when you uproot
plants. Do this slowly and carefully.

Composted manure may be added to the soil substrate to provide
additional trace nutrients, nitrates, phosphates. The disadvantage
would be that there is probably a higher chance of a green water
algal bloom if you disturb the substrate too much. UG filtration
or circulation flow devices would not be a good idea with a soil
or soil/composted manure substrate.

Paul K. has also mentioned adding finely ground eggshells to his
soil compost mix.

Soil and manure enriched substrates have been actively used in 
successful planted aquariums for many years. Perhaps we are only
rediscovering them with recent interest in aquatic plants in the
last few years in the hobby. :-)