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Re: Activated carbon (was APD V3 #1156

Hello Kim, Louis,

The confusion about activated carbon (AC) is understandable, because
people assume that one brand of activated carbon is fairly much the same
as another. That could be true if one looks at the _adsorption isotherm_
(the "adsorption power" per unit weight) but not necessarily for other

Not all AC is made from the same starting materials. The most common
materials used to make granulated AC are probably wood, bone, coal,
petroleum tar. Actually, any carbon-containing material can be converted
to AC.

Obviously, AC made from animal bones will contain a lot of phosphorus,
that from wood will have substantially less and AC made from
once-distilled petroleum tar -- only traces of phosphorus, if that.

So, one brand of AC CAN contain phosphorus, while another doesn't! If
the AC package in the LFS tells you how great this super-duper brand is,
how happy your fish will be if you use it, but does not tell you what it
was made from -- you are buing a "pig in a poke"! Look for a brand that
tells you that the AC was made from petroleum tar -- it probably
contains less phosphorus than AC made from other starting materials. Or
buy a brand that tells you straight out how much (leachable) phosphorus
it contains.



> Date: Fri, 16 Jul 1999 11:24:39 -0400
> From: "Louis Lin" <lhclin at aw_sgi.com>
> Subject: Re: activated carbon
> Kim Bryant wrote:
> > Some recent posts have mentioned that activated carbon can be used to remove
> > the discoloration from aquarium water.  They've got me wondering.  I haven't
> > used activated carbon in a long time - even when I thought it would be nice
> > to quickly reduce protein levels - because I had it in my head that
> > activated carbon leaches phosphate into the water.  Now I'm wondering if
> > this idea is based upon some good evidence, the source of which I've long
> > forgotten, or if it is based, perhaps, on a dream.  So I would appreciate it
> > if someone would set me straight - privately, if it is too mundane a matter
> > for the digest. Does activated carbon leach phosphates into the acquarium
> > water?
> You didn't dream it up.  Phospate leaching is a real possibility.  There
> are some archived articles about it:
> http://nucalf.physics.fsu.edu/pfohl/Fish/Marine/General/gac
> I also remember the ad of Hydrocarbon (a brand) emphasizing that
> their brand does not leach phospate like some other brand does,
> with some test tubes showing the result.  If you have some old
> fish mag, you should be able to find it.  Of course, being an
> ad, take it with a grain of salt.
> If you have a phospate test kit, it is easy enough to test phospate
> by putting the carbon in water for a day or so and compare with
> the control.
> OTHO, I can't pull off my head how much phospate carbon can
> potentially leach, but if your tap water and/or fertilizer already
> contains phospate, may be carbon is not a big source to worry about.
> Louis Lin