Path: utzoo!hoptoad!amdcad!pyramid!decwrl!labrea!husc6!yale!Ram-Ashwin
From: Ram-Ashwin@cs.yale.edu (Ashwin Ram)
Newsgroups: alt.aquaria
Subject: Re: what does carbon in a filter do? (AND) Re: "Brown and smelly"
Message-ID: <28329@yale-celray.yale.UUCP>
Date: 3 May 88 02:33:55 GMT
References: <9178@agate.BERKELEY.EDU> <4268@super.upenn.edu>
Sender: root@yale.UUCP
Reply-To: Ram-Ashwin@cs.yale.edu (Ashwin Ram)
Distribution: usa
Organization: Computer Science, Yale University, New Haven, CT 06520-2158
Lines: 49
In-reply-to: ephram@violet.berkeley.edu (AND) levine@eniac.seas.upenn.edu

In article <9178@agate.BERKELEY.EDU>, ephram@violet writes:
>                          The store I used to go to placed nylon bags full of
> carbon in the tank.  When asked the proprietor would mumble something about
> helps clean the ...  I went to another store and heard much the same think
> "It cleans the water".
> 
> All of this has been very unsatisfactory, so I ask, What does charcoal do
> in 1) a external box and floss type filter? and 2) in tandem with my U-G
> filter?

I'll take 2 first.  If you mean the little filter plugs that go on the outlets
at the top of the UG lift tubes, probably nothing except reduce the flow of
water.  But 1 is a different story:

Activated carbon (or activated charcoal) is produced by the carbonisation of
plant matter.  It's good as a filter medium (if prepared properly) since it
adsorbs coloids (e.g., proteins, dyes, organic acids, water-soluble drugs), and
gases such as chlorine and ozone.  Will not adsorb ammonia, nitrite, nitrate.

(Adsorption is the adhesion of gases/dissolved substances to the surface of a
solid body without a chemical reaction.)

Activated carbon filters must be cleaned regularly.  Spent filters begin to
release poisonous fission products and ions which eventually begin to creep back
into the aquarium.  Also, spent filters contain oxidisable substances in high
concentrations, which tend to remove the oxygen from the water.

In article <4268@super.upenn.edu>, levine@eniac (Jonathan M. Levine) writes:
> I have just a 10 gallon with a box filter...and I've been changing the floss
> every time it gets brown and smelly.  Is this not what I'm supposed to do? 
> How often is one supposed to change the charcoal/floss in a box filter?

You can't regenerate activated carbon.  How often you need to replace it depends
on how many fish you have, how large (and dirty) the tank is, and so on.  Once
every 2-4 weeks is a good estimate.  One way to test whether the adsortivity has
reduced is to put a drop or two of a dye that the carbon would adsorb (such as
methylene blue) right behind the filter cartridge.  If you see blue trickling
out with the water on the other side, you probably need to replace the carbon.

As a rough guide, try turning the flow rate on maximum and check if all the
water passes through the filter.  If the filter is clogged, the water will
accumulate on the input side and begin to trickle back into the tank without
passing through the filter medium.  (Depends on the design of your filter.)

-- Ashwin.

ARPA:    Ram-Ashwin@cs.yale.edu
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