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Preliminary comparison of Eco-complete & Onyx -- or - Shades of Grey

Onyx, as you know by know, is grey.  About the color of an
oldfashioned Blackboard that's been well used and wiped
down, leaving a film of chalk over the surface.  It's very
porous--I would guess mircoscopicly so.  

Eco-complete is gravel with a texture like small silica
granules or rocks.  The size varies widely from about 3 mm
to fines, but not nearly so fine as Onyx, which has
matrerial the size of powder -- hence it's reputation for
needing lots of rinsing ;-) .  The Eco *is* virtually
dustless.  I suspect it's hardness is part of that plus the
fact that it is packed in water, which might help act as a
lubricant during shipping.  I suspect it's more a cas of
the former than the latter -- I've had Fluorite arrive
slightly wet inthe bag and it was still full of fines and
dust.  Eco is so dustless that I smashed some with a hammer
and put the  remains under an IntelPlay microscope (how's
that for science ?)  to see if the color was a an epoxy
coating.  It appears to be black through and through.  I
could not discern whether it does or doesnot have any
coating to minimize.

It's hard to compare volumes per weight.  The Onyx arrived
bone dry.  The Eco comes in water, just enough to make it
workable, hold it's shape if you form it in your hand.  So
a lot of it's weight is water.  In the side by side 20 gal
tanks, 2 bags of Eco in one tank gave 2.5" of gravel abbove
the bottom glass; 3 bags of Onyx in the other tank gave 3"
of substrate above the bottom glass.  So 2 bags of Onys
would have yielded a 2" layer compared to 2.5" for the Eco.
 Both brands costs about $13 per bag plus shipping if you
shop carefully.

Eco does not seem to be very porous.  The bag calls it a
'macroporous' substrate, by which I assumed it meant that
the particles have spaces between them, not that the an
individual grain or rock is porous.  It supposed has a
whole list of minerals, but I have no idea how any of it
might be made available to plants or if it is sealed into
the grains.  I don't know what CEC value this gravel has.

The color of Eco is black in the bag.  Once in the tank
under light (I'm using an AH Supply 36 watt running at a
108 ballast factor), it is slightly more grey looking than
in the bag.  But detectably darker than Onyx.  Not as black
as the epoxy-coated gravel you can by in the lfs from Estes
or TopFin, but nearly so.

Because it is known that Onyx buffers upwards -- I think,
like true onyx, it is calcite based -- I put a layer of
sphagnum peat on the glass under the Onyx.  I did not do
this in the Eco tank.  I expect Eco to have no direct
effect on pH.

We'll see what happens.  I plan to post follow-ups on the
mail list at 


which is the Dallas Ft. Worth Aquatic Plant Club site --
the group hosting the 2003 AGA Convention.  Obviously, you
don't have to live in Texas to be a member.  I didn't hold
it against them that they'd have someone like me as a
member, you shouldn't either ;-)


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