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Re: Activated charcoal (Aquatic Plants Digest V3 #1411

Hello Joo,

Activated charcoal adsorbs preferentially organic compounds. The more
double bonds and/or aromatic rings a compound has, the chances are that
it is better adsorbed. Because the yellowish color of aquarium water is
usually caused by (aromatic) humic acids, it is well adsorbed and the
water made colorless.

However, ALL surfaces adsorb also ionic species, even glass adsorbs some
ions. So, SOME of the trace elements will also be adsorbed. But the
adsorption is governed by equilibrium, which favors the solution, so
this adsorption will not be a continuous drain.

Furthermore, after a short time, bacteria settle the charcoal, and form
a very efficient biological filter. It builds down complex organics,
freeing some charcoal surface for more adsorption. A patent was issued
on that process.

A caution: ALL activated charcoals are NOT ALIKE! Even the same brand
can change over time, so the best advice is to try it over several weeks
and observe the results.



> Date: Thu, 25 Nov 1999 12:26:47 +0800
> From: "Joo Tan" <zoologist at mailcity_com>
> Subject: Activated Charcoal
> Hello folks,
> Does anybody know what exactly does the activated charcoal absorbs?  I came across a few reference books as well as websites that said activated charcoal is no good for a planted tank as it absorbs all the nutrients and trace elements from the water.  On the other hand, there are a few people that use activated charcoal in their planted tanks.
> So is there anybody out there that did some researches on what exactly does the charcoal do to the water?
> Regards,
> Joo