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Re: More on Filter less Plant Tanks

I've been sitting back on this one, but I'll make a few comments which
support Karen Randall's posting in Digest 873.

James Purchase wrote (in part - I've heavily edited):

>A lot would depend upon which is better at scavenging ammonium ions from the
>water column - plants or bacteria. I don't know the answer to that one, and
>would appreciate comments from anyone who does.

I don't know the answer to this one, but my experience of removing the
filter material from my tank leaves me believing that the plants are awful
good, and will support quite a reasonable bioload from fish.

>I just came across an article written by Diana Walstad and published in the
>April 1994 issue of FAMA (Aquatic Plants Prefer Ammonium Over Nitrates)
<big snip>
>Diana concluded by stating that in a heavily planted aquarium, in the
>absence of a separate filter, a moderate overload of nitrogen would not lead
>to NH3 toxicity to fish but rather a slow accumulation of nitrate NO3.
>This last bit I don't understand totally - if all of the nitrogen input is
>in the form of NH3 or NH4+, and is used by the plants for growth, there
>should be no build-up of nitrate.  <snip balance of post>

What's going on is simple. An overload of nitrogen means the plants aren't
taking up all of the ammonium. That leaves some in the tank and bacteria in
the tank (they're  not all in the filter) will convert that to nitrate in
the same way as would occur in the filter. The bacteria we cultivate in
bacterial filters already exist in our tanks - filter medium just supplies
a highly congenial hotel in which they can shack up and continue to
propogate their species in free room and board :-)

David Aiken