03-03-2003, 03:39 PM
Carbon in filter: Really absorbs liquid fertilizers??
In article ,
If carbon removes heavy metals, then would it remove some of the trace
elements that we add to the tanks?
It could, and that's what people worry about. That's why many people remove
the carbon from their filters. (If you have something like a Whisper, where
the carbon's built into the pad, there's alternative media sold for it, that's
I did an experiment several years ago when I first started with a
planted aquarium. I added a controlled amount of iron fertilizer and
tested for its presence 24 hours later. Without activated carbon, I had
a reading of between 0.1 - 0.3 ppm. With carbon in use, I never
detected any. From this I concluded the carbon removes the chelated
iron (the form present in aquarium fertilizers).
In the 9+ years since I did these tests, I have not used activated
carbon except to remove medications after treatment or to clear the
water. Occasionally, the water takes on a slight yellow cast, and the
carbon removes it quickly. Of course, after the carbon treatment, I add
some extra fertilizer. I use PMDD.
As a Chemical Engineer, I had contacts with companies who make activated
carbon, and they said my findings were consistent with tests they had
The catch, if any, to this is that the carbon's capacity to remove iron
is limited. So, if you leave it in long enough, it will not remove the
iron or anything else. Which is why some people who use it in planted
aquaria say it does not remove the fertilizer.