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Re: Sand in substrate


I've used sand a couple different ways, and I have some observations.

1)  With the exception of some initial settling there should be no
long-term compaction.  Sand doesn't compact anymore than gravel.  If you
tried contouring the substrate and didn't use something to keep the sand
in place then the sand will gradually shift from areas with thick
substrate to areas that initially had thin substrate.  Eventually you'll
have a flat substrate.

2)  Plant roots have no problems penetrating most sand, but very
fine-grained sand may be a problem for some plants.

3)  You can get anaerobic areas under driftwood and sometimes under rocks
about as easily with gravel as with sand.  My plants act like that's a
good thing, as I invariably find that they send their roots into those
zones. Plants in at least some genera (val and barclaya, specifically) do
better when they can root into those zones.

4)  Very fine sand should probably be avoided.  I used some very fine,
unwashed sand from the local river -- much finer than any play sand or
construction sand I've seen -- and found that mulm could not settle
through the sand.  Problems mounted over time and eventually the buildup
of very fine mulm in the top part of the sand and in the gravel just above
the sand layer caused me to tear the tank down and rebuild.  Some plant
preferred to spread their roots above the sand layer,while others roote
through it.

5)  I now always mix some sand with the gravel in my aquariums to provide
a more natural variation in grain size in the substrate.  I find that
visually more pleasing and I think it promotes better root development.  I
have no problems with sand mixed into the gravel.

Roger Miller