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Re: [APD] carbon filter and trace elements

The conventional wisdom is that activated carbon removes trace minerals from water. I used to believe this poppycock, too, then decided I preferred to subscribe tothe laws of physics.
Activated carbon seems to be poorly understood and what is written about it seems even worse, on the whole. 
Activated carbon is not an effective way to remove minerals. There are some exceptions for some heavy metals but for even for those it is not the filtration medium of choice and generally, it's effectiveness is mostly limited to removing organic compounds by adsorption. This is a slow process and the more slowly the water passes through the carbon, the longer the exposure, the higher the amount of adsorption. 
There is some confusion about whether it removes iron from the water.I believe it might hang onto some iron if it grabs the chelator that's hanging onto the iron. But chelators break down reasonably quickly in the presence of all the other stuff that gets caught in the carbon. Actually, activated carbon is a totally inefficient method of removing iron from water.
Activated carbon also works as a "catalytic" to very quickly bind negative ions such as chlorine ions in the water, which is a whole diff process. This process is much faster than the adsorbtive filtration. It doesn't hold positive ions at all, in fact it repels them.
So, it doesn't do squat for capturing the "metal" part of salt compounds, sodium, calcium, magnesium, etc.
Once the carbon has had aquarium water running through it for a few about a week or so, it's loaded with biofilm and pretty much is acting as a very expensive mechanical and biofilter medium. 
It won't remove orthophosphates or inorganic nitrates.
If you check the bottle contents, you'll see that micronutrient trace elements for plants are not organic compounds.
Activated carbon isn't necessary if you have other reasonable means of filtration and especially if you are doing large, regular water changes. In that case, It's a bit like buying very expensive silk socks and then wearing long pants that cover past your shoes. You know you spent the money, but it doesn't accomplish much else.  ;-)
* * * * * * * * * * * 
The Northeast Council of Aquarium Societies (NEC) celebrates its 50th year of service at its 31st annual convention, April 7-9, 2006 -- including *An Evening with Aquarium Legends*.
Read the speaker list, then download the registration form, and get set to join the fun at what promises to be the year's biggest tropical fish convention.
And while you're there, attend the AGA's annual meeting Friday afternoon (2-4pm). This year's speaker is Claus Christensen, Tropica's Managing Director. 

----- Original Message ----
From: Joel Fizette <sentientpuppet at gmail_com>
To: aquatic plants digest <aquatic-plants at actwin_com>
Sent: Saturday, February 25, 2006 5:22:49 AM
Subject: [APD] carbon filter and trace elements

How much does a carbon filter really affect the trace elements in a planted
tank? should I use one or not?
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