[APD] RE: Aquatic-Plants Digest, Vol 4, Issue 72

["Thomas Barr" <tcbiii at earthlink_net>]

>From: "Steve Pushak" <teban at powersonic_bc.ca>
>Subject: [APD] Re: Carbon filtration, & the FAQ
>To: "APD" <aquatic-plants at actwin_com>
 
>Conventional wisdom about the use of activated charcoal filtration is that
>it is unnecessary or harmful in that it might remove chelated trace metals
>from the water.
 
>Should the FAQ entry be amended?
 
>Steve P

I really don't think activated carbon is all that bad, just don't keep on
using fresh carbon each month etc.
After a month it is spent and becomes biomedia.
Carbon may remove metals, but cation exchange is much better for this
removal. 

I think over all, since plants need less than we dose of these TRACE
metals, the metals make it to the plants beofre they are removed by the
activated carbon.
Metals often get comlexed with organics(This will tie back into the DOC
issue) and also inorganic forms also may precipitate and fall out of
solution.

I think it's less IMPORTANT to worry about things that will remove trace
metals and more important to make sure there's enough trace metals for the
plants.

UV, compexation with Inorganic and Organic compounds, activated carbon all
bind the iron and other traces or make them unavailable in some way.

But a certain level of iron dosing residual is not going to help you
because often these residuals merely measure total iron (or chelated iron
perhaps).
But the faith of the iron even if Chelated might not be for the plant.

I think getting everything else right first, then adding traces up to the
point where adding more does not help the plants, is the best way to
determine a good iron dosing.

If you add iron etc every few days and enough trace mix, I think carbon,
UV's, etc play a small role.
Iron residuals just don't last long to be meaningful, spikes of iron every
2-3 days works well.

Regards, 
Tom Barr









  


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