laterite alternatives

Jos (of the Vancouver aquatic plants club) wrote:
> The laterite clay is possibly available at Greenbarn Potters Supply ltd.
> 9548-192nd Surrey BC ph.888-3411. I did had them on the phone but they
> don't know Laterite, they have red colored clay (Fe). I don't have time
> to go there yet.

Made a brief phone call to them to discuss the various types of clay
they have. H490 has lots of Fe but also has .01% Barium which may be toxic.
I'm curious if anyone on the APD has any comments about Barium or any
other additives in the various potter's clays.

As an alternative they recommended Terastone which is 16.96 for a 44 lb
box. This sounds like it might be a good choice if you need a sterile
clay with absolutely no humic material. (I recommend you have about
0.5% humic material in the lower layer)

OTOH if we want to duplicate the qualities of Dupla laterite, I was struck
by the extreme similarities between ordinary top-soil and laterite. This
can be used quite safely in the same proportions as suggested by the
Dupla method. (that is used in the ratio of 1:20 soil:gravel in the
lower 1/3 of the substrate). Since top-soil is relatively cheap to obtain
(once you've chose a suitable site to excavate it from) I think it is
quite safe to use a higher proportion of soil to gravel.

From the perspective of H2S production, as long as the aquarium is well
planted, the experts suggest that there will be no problem using 100%
top-soil. We are currently reviewing what it would take to create an
environment with H2S concentration sufficient to be concerned but my
feeling is that you would need to have a substrate containing greater
than 25% well-composted manure and even this is probably manageable if
planted with lots of sword plants and given good light!!!

If using soil or any other medium which contains organics (except peat)
there is a chance that there will be a certain amount of phosphates
contained within the soil. This is actually good because plants do best
with the phosphate supply in the substrate; it cannot be safely added
in solution. It can however create a problem with green water when
initially setting up the tank. Paul Krombholz said he doesn't think
it will really be an issue when using ordinary top-soil. I think it's
more critical with manure enriched substrates. Anyway, here is
his procedure:

Steve, June 13, expressed concern about high concentrations of nutrients
released by composting.
I am concerned about that. too,  I don't think it is good to have high
concentrations of soluble nutrients in the soil of aquatic plants.  In
theory they can cause osmotic damage to the roots of aquatic plants, and
nitrates in the soil can prevent, at least until they are used up, the
desirable reducing conditions that make iron soluble.  Besides,  the
nitrates are wasted if they get converted to atmospheric nitrogen.   If I
have soil that I think has a lot of nutrients released by composting, I
extract the nutrients before using the soil for growing aquatic plants.
The latest TAG describes two methods I use to extract nutrients from soil.
Just ordinary soil from the woods shouldn't need to be extracted.  it is
already thoroughly extracted by the rains and the plant roots.  I shouldn't
think that there would be any need to extract composted soil-peat mixes
because there are such small amounts of mineral nutrients in peat.  It
might be advisable to extract soil-manure mixes before use.  I think that,
for beginners, soil-peat mixtures would be 'safer'.

The "soil-soup" method where soil is collected and water is slowly added
with much mixing until you have something like thick soup, which is then
run through window screening or a rice strainer, produces a safe product.
The screening filters out all the roots, worms and other critters, and
other "raw" pieces of organic matter that might cause a large oxygen
demand.  About a quarter inch to a half inch of the soup is placed in the
bottom of the tank or planting tray and covered with about a half to one
inch of gravel.  Water can be added with precautions to prevent stirring up
the gravel, and almost no cloudiness will develop.  The gravel can be put
on top of the soup, and then everything can be allowed to dry out.  The
soup turns quite hard, but when water is added, it gets soft again, and the
plants seem to grow just as well.  If the soup has been allowed to dry out,
the chances of any cloudiness developing when water is added are much less.
The soup is relatively low in organic matter, and I have found that, when
a tray becomes packed with roots, low-level iron deficiency develops, and
additions of soluble iron stimulate growth.  Soil-peat mixtures or
soil-manure mixtures beneath gravel seem to be able to supply iron for a
longer time.  I have not seen any tannins come from soil-soup, but I have
seen tannins get into the water from soil-manure and soil-peat mixtures.  A
water change gets rid of them, and they don't seem to come back.

The development of green water and/or an increased in soft attached algae
as a result of using soil should not be considered a serious problem.
Perhaps this does not occur with laterite because laterite is a tropical
rain forest soil which is extremely low in soluble nutrients and organic
matter.  Tropical rain forest soils have almost no humus, and virtually all
the solible nutrients are locked up in the biomass of the vegetation.  When
we use our local soils, which have more humus and nutrients, these
nutrients are going to get into the water and stimulate algae growth.  The
nutrients seem to get into the water quite quickly.  I have put trays of
soil soup made from subsoil covered with an inch of fine silica sand in a
tank and have seen greening and increased algae growth in just two days.
Over and over again, I get evidence that nutrients in soil or soil soup get
into the water quickly, even if the soil soup is covered with an inch of
gravel or even sand, which ought to impede diffusion more than gravel.

Adding trays containing soil or setting up a tank with some soil under the
gravel is going to put some nutrients into the water, but there are
techniques for keeping green water or other forms of algae from taking over
for any long period of time.  These would include: (1) keeping the fish
load really low or starting with no fish until the plants get the upper
hand.  (2) cutting back on the light.  (3) use of snails and algae eating
fish,  (4) If green water won't go away, CO2 enrichment and actually adding
nutrients can get the aquatic plants to grow enough to get the upper hand.
(5) use of floating plants, such as Ceratopteris to shade out the algae.
(6) use of Daphnia, provided you can get all your fish out.  (Having your
plants in trays helps when you are going after that last fish who has
figured out just what you are trying to do with that net.)  (7) use of
diatom filter to clear up green water, although I bet this is a temporary
measure that may have to be repeated until the plants get the upper hand.
(8) other methods that I don't know about.

-end of quote-

From my experience, the use of a diatom filter is the best for the
following reasons:
1) it's very fast
2) doesn't deprive the plants of light or nutrients

I was able to combat a moderate green algae bloom using PMDD
additions and a heavy Salvinia cover. It took several weeks
and the effects on the other plants especially Crypts was quite
severe. The Crypt wendtii lost about half their leaves (which I
expect to grow back). Hygrophila stricta lost all but the top
leaves due to extreme nutrient shortages while the green water
algae was actively soaking them up. I also advocate a shorter
lighting period which plants can use more effectively than the