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Re: More on Filter less Plant Tanks
>Date: Fri, 26 Feb 1999 13:54:37 -0500
>From: "James Purchase" <jpurch at interlog_com>
>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.
The problem is that the concept was grossly oversimplified. The assumption
is that nitrifying bacteria are only in the filter - "no filter, no
nitrifying bacteria". This is not correct.
Nitrifying bacteria occur everywhere in an aquarium; on the gravel, on the
glass sides, on equipment, on plant leaves, even in the water. Biological
filters are useful in that the biomedia provides for a higher concentration
per volume of bacteria.
Dr. Alfred Gianascol, in "Water Chemistry in Closed System Aquariums"
(1987), demonstrated that in a typical aquarium [without plants], the
actual filter only provided about 15% of the total nitrification. The
biofilm on the glass and gravel provided the rest.
So, you can safely assume that there are in fact huge numbers of nitrifying
bacteria in even the most densely planted tank and that they will happily
convert any ammonia/ammonium that drifts their way into nitrate. They DO
compete with the plants for nitrogen and WILL generate nitrate.
I conjecture that tanks with very low nitrates have some form of
denitrification going on - either the plants are not getting their fill of
ammonium and are utilizing nitrate or denitrifying bacteria are at work (or
George Booth, Ft. Collins, Colorado (booth at frii_com)
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