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Re: adsorbants

> From: "Mark Shelton" <mark_shelton at pobox_tbe.com>
>      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 ?

I assume you are refering to the loss of ionic micronutrients like iron.  
Most of those are lost as humic acid chelates, so anything that removes 
yellow color from the water is going to remove the humic acids.  Some of 
the adsorbents you mentioned are substantially weaker than activated 
carbon, so their capacity and kinetics of removal will be slower.  That 
might be of some help.

I'll make a comment here that I've made about reef systems.  The goal of 
keeping one of these tanks is to create a beautiful display, not to use 
trace elements in the most efficient way.  If small quantities of carbon 
pulls out some micronutrients, I'd just add more of those trace elements.

It will be quite a battle to keep up the iron concentration in a system 
where there is a substantial amount of yellow color to the water.  Once 
the yellow is gone, you should have a somewhat easier time of it.