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carbon filtration

---------- Forwarded message ----------
From: Stephen.Pushak at saudan_HAC.COM
Subject: carbon filtration
To: aquatic-plants at actwin_com
Date: Thu, 06 Mar 1997 2:39:46 PST

> From: "Mark Shelton" <mark_shelton at pobox_tbe.com>
> Subject: Chemical Filtration
>      Like most people (I think) on this list, I do not use any form of
> chemical filtration (e.g., carbon, etc.) for fear of plant nutrient loss.
> Between weekly or biweekly water changes, the water becomes noticeably
> yellowish and dingy as expected without the carbon. I would certainly like to
> use a filtration media that would yield a continuously colorless water. 
> So, is
> anyone using carbon, perhaps in small amounts, in their plant tanks without
> causing significant nutrient deficiency ? If not, are there any other 
> chemical
> media that can be used successfully (e.g., Purigen, Renew, etc.) that are 
> more absorption/adsorption selective ?

It is true that carbon filtration will remove chelated Fe from your
water but it won't affect Fe available in soil substrates. Since it is
not important to maintain nitrifying bacteria in a filter, you can
simply turn it off for a few days after you add a dose of chelated Fe.
This will give the plants the opportunity to absorb a surplus of Fe
which they will store and use for several days. I think carbon filtration
is the best for removing yellow organic material from your water but
it may not be best to filter it continuously as it also serves useful
purposes to inhibit algae and bacteria. In excess it also may inhibit
some of your plants and some compounds like phenol are not healthy for
fish in large quantities either.

I run my filters intermittently to remove suspended particles that make
the water cloudy and if I suspect an excess of Fe which might contribute
to an algal bloom. Unless I have high levels of ammonia, I rinse the
filters in hot water to kill the nitrifying bacteria since I want the
ammonia to be available for the fish. Usually this is not a problem
but it is wise to monitor ammonia when making changes in an aquarium
_especially_ with a new, fertile substrate.

Carbon filtration should not affect availability of any major
nutrients but might remove trace chelated Mn same as iron. I suppose
it is possible to remove chelated Cu and Ca which could be complexed
with natural organic acids but I don't know if this would make much
difference. If you added free chelating agents to reduce excess Cu
you might just remove primarily Ca which I think has a higher
affinity for chellants. Chemists, keep me honest! ;-)

Summary: use carbon filtration for a few days to cure water yellowed
by dissolved organics and then resume dosing micro nutrients afterwards.
Or if your micro nutrients are not too expensive just continue dosing;
some of it can still be absorbed by plants.

Steve in Vancouver (busy preparing for a new project and new computer