[Killietalk] Re: Poly Bags

[YoHoHo at aol_com]

In a message dated 9/2/2003 5:36:42 PM Central Standard Time, 
killietalk-request at aka_org writes:
Message: 7
Date: Tue, 02 Sep 2003 14:04:43 -0400
From: "M. Frauley and G. Elson" <fraulels at videotron_ca>
Subject: Re: [Killietalk] Poly Filter
To: killietalk email list <killietalk at aka_org>
Message-ID: <3F54DBBB_57104D65 at videotron.ca>
Content-Type: text/plain; charset=us-ascii

I know the cichlid crowd often swear by poly-filter for shipping, but
one thing that strikes me is that whenever I have received cichlids with
it in the bag, they've been on the road less than 24 hours. We tend to
trust killies to survive much longer periods in very small amounts of
water, especially when they go to shows or auctions.

My question is one posed by an English teacher on a list full of
chemists... do the types of absorbent materials and resins sold in the
hobby ever leach back the chemicals they have picked up, or do they
simply reach their 'capacity' and cease to function?

Gary Elson
"Ion exchange" materials work on and "obey" the principles governing chemical 
reactions, i.e., they move in the direction toward equilibrium conditions.  
Simply said - When they are new or fresh, the concentration of contaminants is 
higher in the water than on the poly filter, so the contaminants are adsorbed 
by the polyfilter.  When used in a flowing water system like a flow thru 
filter, the polyfilter will continue to adsorb contaminants until all the available 
sites on the filter material are used up.  This is the maximum capacity of 
that filter.  If the water stops flowing and the filter is allowed to sit 
stagnant, the equillibrium changes because the polyfilter is now "more contaminated" 
than the water around it, and the materials it had adsorbed will now be 
released back into the water until equilibrium is again reached.  That means if the 
water flow is shut off, you are recontaminating the surrounding water.  "BTW, 
this is even true in the small ion exchange filters used on drinking water 
taps, so always run one glass of water out before you collect it".

In a shipping bag, the conditions are stagnant, so the polyfilter will 
continue to adsorb materials up to the point where equillibrium is reached. If the 
water contains more contaminants than the capacity of the polyfilter, then it 
just stops adsorbing them because it is full or "used up".  At that point 
equillibrium is reached, so the polyfilter will not release the contaminants it had 
adsorbed unless something happens to change the "equillibrium".  Perhaps a 
significant change in temperature could cause that, but normally the 
contaminants should "stay put"

I hope this lesson is clear to everyone.  There will be a closed book test at 
your next local fish club meeting, (which is at my house this Sunday).


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Frank Carriglitto
AKA #08234, ChiKA, WAKO