Laterite Substrate
by Robert Paul Hudson
from Robert's web site in Salem Oregon: Aquabotanic.com
Aquarticles
Laterite is a soil formed by decaying rocks weathered by tropical heat and centuries of
heavy rain. This process strips the soil of all nutrients except oxidized iron. On land
plants cannot grow in this type of soil, but in tropical Asia laterite run-off is found in
waterways, providing iron to aquatic plants. Laterite rocks, (not soil) can be found in
areas of North America. The term laterite and clay are often confused. They are not one
and the same.
Dupla was the first commercial company to market laterite for aquarium use, and state
on their web site that there are several grades of laterite soil, not all of which are
beneficial to the aquarium. They claim to use a grade that has been tested and approved
for aquarium use.
I have used Duplas Duplarit, but there are alternative laterite products out there,
tested or not. One box of Duplarit is good for a 55-gallon tank. Duplarit also comes in
balls that you can break into pieces and push into the gravel, but for a new tank I prefer
to use the granular form. First Layer Pure Laterite is another alternative.
Using it is simple. Simply mix the box contents with an inch layer of gravel, and then
top with 2" to 3" of straight gravel. I also add a thin layer of sphagnum peat
before adding the top layer of gravel. The peat provides a slight increase in iron, a CEC
medium, and the organic acid helps make the iron more accessible to the plants. Only a
very small amount should be used, because too much decaying organic material in the
substrate can cause all sorts of problems.
If you plan on having fancy terracing, and sloping substrates, then plan the layout
ahead of time and use the laterite accordingly. It is important to keep it well covered in
the substrate to prevent it from entering the water. If your substrate foreground will be
sloped so low that it is less than an inch deep, do not put laterite in the foreground. If
back areas are deeper than 4 or 5 inches, then layer the laterite in the middle of the
substrate.
Any type of undergravel filter is not advisable with a laterite and peat substrate for
reasons that should be obvious! The UGF will dump the laterite and peat into the water
creating an unbelievable mess!
Laterite is primarily beneficial for deep-rooted plants and heavy feeders, such as echinodorus
and cryptocoryne species. Most stem plants and ferns will take the majority of
their nutrients from the water.
A laterite substrate should last for years and can be supplemented with regular doses
of liquid chelated iron and mineral trace elements.
Have questions? Email me at robert@aquabotanic.com
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