Author: Dr. L.E. Freese
How
many people have started an aquarium to only go through the heartache of
losing the fish a few days or weeks after acquiring them?
At the Rand Show recently,
the most common answer to the question “ Do you have any fish at
home?” was “Yes, but they all died!”
In the discussions that
followed a general lack of understanding of the ecological system of an
aquarium was revealed. The nitrogen cycle, which is the breakdown of
toxic ammonia into relatively harmless nitrate, is one of the most
significant cycles that occur in the aquarium.
NITROGEN CYCLE
Ammonia is found in the urine
and faeces of the fish and it is also one of the chemicals that is
formed by decaying plants and food that has not been eaten by the fish.
(Therefore beware of over feeding.) The ammonia
is broken down by down to nitrite
by Nitrosomonas bacteria and Nitrobacter
bacteria break the nitrite down to nitrate.
The plants use nitrate to grow and the plants in turn are eaten by the
fish. The nitrifying bacteria require oxygen, warmth, food (in the forms
of ammonia and nitrite) and surfaces onto which they can adhere to, to
survive.
In a new setup the tank is
sterile and contains no bacteria and no ammonia. The bacterial colonies
need time to multiply and this can take 2-6 weeks and in some cases up
to 12 weeks. As the bacteria need ammonia to grow, usually 1 or 2 fish
are introduced to the aquarium to provide the ammonia (the aquarium is
never fully stocked at the beginning). Only when an aquarium is fully
matured should you introduce new fish and this should also be done
slowly and not all at once. If fish are added too quickly or too many at
one time, an ammonia spike occurs 3-5 days later and the toxic levels of
ammonia lead to the death of the fish. Doing partial water changes can
reduce toxic levels of ammonia.
There are ways of speeding up
the aging of the aquarium and those are the addition of gravel or filter
material of an established tank or adding the commercially available
dormant bacteria.
CLEANING
When cleaning the
tank/aquarium, it should never be totally sterilized (boiling the stones
and removing all the water) as this destroys the bacterial colonies. Nor
should the filter and the aquarium décor (which includes the gravel) be
cleaned at the same time. This would cause toxic levels of ammonia and
nitrite to occur and you will have stressed unhealthy or even dead fish
to contend with.
Cleaning should involve the
cleaning of the front glass panel to remove the algae and dirt (remember
that the utensils used should be free of chemicals such as soap).
Removal of 25-50% of the water at least every 2 weeks is required to
remove the build up of nitrates in the water. Lastly the filters should
be washed in the water that has been removed from the tank in order for
the bacteria not to be destroyed by the chlorine contained in tap water.
When doing the water changes, do not forget to treat the water for the
removal of chlorine and heavy metals.
The fish hobby should be a relaxing and enjoyable one
and if the proper procedures are followed when cleaning the tanks, it is
almost hassle free.
August 2001
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