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BIOLOGICAL FILTRATION
The Biological filter is designed to encourage the growth of beneficial
bacteria and other organisms that are responsible for breaking down
harmful fish waste. These bacteria are known as 'Nitrifying Bacteria'
and they naturally occur in the process known as the 'Nitrogen Cycle'.
The sequence of events in this cycle are Ammonia produced from fish
waste, this is converted into Nitrite, which in turn is converted
into Nitrate
When a new tank or system is set up, there are insufficient numbers
of these Nitrifying bacteria present to break down the fish waste.
So a period of 'Maturing' the biological filter is needed. The length
of time required to develop a full compliment of Nitrifying bacteria
depends a lot on temperature. At 25c (77f) the process could take
between 2-6 weeks, at much lower temperatures of say 10c (50f) it
will take considerably longer.
It is recommended that you use a commercial liquid maturing agent
to start the Nitrogen cycle. The maturing agents will actively promote
the growth of the nitrifying bacteria on it's own. When using this
method, fish are not required to complete the nitrogen cycle. As
we explain later, fish should be introduced after the tank is mature.
During the maturing process it is important to monitor both Ammonia
and Nitrite levels. In the early stages the first to show will be
the Ammonia, this should be monitored daily with a test kit to see
the levels rise, then peak, and begin to fall off. As this fall
off occurs it indicates that the levels of the bacteria responsible
for breaking down ammonia is increasing and beginning to mature.
As the ammonia levels continue to drop the by-product of this part
of the process is Nitrite, it is at this point that you should now
monitor the Nitrite levels, as this will also rise, peak and then
fall just as the ammonia did. When both the ammonia and Nitrite
readings have fallen to zero, then the biological filter is said
to have a full compliment of nitrifying bacteria and so is mature.
The end product of the process is Nitrate. At low levels nitrate
is non-toxic but must not be ignored and allowed to rise to troublesome
levels. This subject is covered later on.
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