14 Denitrators
Description
This article is from the Aquaria: Filters FAQ, by Bruce Hallman.
14 Denitrators
Another specialized type of filter is designed to help in the control
of the accumulation of nitrates, the end product of the neutralization
of ammonia by the biological activity of bacteria. These fall into two
categories, the anoxic bacterial, and the plant/algal scrubbers
(discussed in the next section). It has been discovered that colonies
of bacteria which grow in oxygen poor environments can be harnessed to
biologically consume nitrate, and release harmless nitrogen gas. This
method is achieved in one of two ways. The process was first developed
in the 1980's through the use of a box system, coil, or porous foam
block which allowed very slow transmission of nitrate-laden water.
Inside the box/coil/foam, sugar was placed, and the slow passage of
water quickly became anoxic. In these anoxic conditions, bacteria
would grow and consume excess nitrate. Many aquarists have reported
failure in their attempts at this type of filtration.
More recently, hobbyists have developed similar anoxic conditions
below plates at the bottom of their tanks buried in fine sand. In the
saltwater systems, these sand beds are referred to as "live sand". In
freshwater planted systems, fine grain substrates are allowed to
develop anoxic zones which probably also have a denitrification
capability.
The Berlin Method of reef aquariums involves the use of large
quantities of live rock harvested from tropical reefs. Aquarists
report good nitrate control in live rock systems, which, though not
well understood, probably involves the denitrification of the nitrates
within the interior of the rocks. Another school of thought is that
the heavy growths of calcareous algae on the live rocks in Berlin
Method reef aquariums consume nitrate.
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