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Older aquariums also go through
periods during which the bacterial colonies fluctuate. Failure
to understand this process is the largest contributing factor
to the loss of fish. Learning what it is, and how to deal with
critical periods during the nitrogen cycle, will greatly
increase your chances of successful fish keeping.
The Waste Problem
Unlike nature, an aquarium is a closed environment. All the
wastes excreted from the fish, uneaten food, and decaying
plants, stay inside the tank. If nothing eliminated those
wastes, your beautiful aquarium would turn into a cesspool in
no time at all.
Actually, for a short period of
time, a new aquarium does become a toxic cesspool.
The water may look clear, but
don't be fooled, it's loaded with toxins. Sounds awful,
doesn't it? Fortunately bacteria that are capable of
converting wastes to safer by-products, begin growing in the
tank as soon as fish are added. Unfortunately there aren't
enough bacteria to eliminate all the toxins immediately, so
for a period of several weeks to a month or more, your fish
are at risk.
However, you need not lose them.
Armed with an understanding of how the nitrogen cycle works
and knowing the proper steps to take, you can sail through the
break-in cycle with very few problems.
Stages of the Nitrogen Cycle
There are three stages of the nitrogen cycle, each of which
presents different challenges.
Initial stage:
The cycle begins when fish are introduced to the aquarium.
Their feces, urine, as well as any uneaten food, are quickly
broken down into either ionized or unionized ammonia. The
ionized form, Ammonium (NH4), is present if the pH is below 7,
and is not toxic to fish. The unionized form, Ammonia (NH3),
is is present if the pH is 7 or above, and is highly toxic to
fish. Any amount of unionized Ammonia (NH3) is dangerous,
however once the levels reach 2 ppm, the fish are in grave
danger. Ammonia usually begins rising by the third day after
introducing fish.
Second stage:
During this stage Nitrosomonas bacteria oxidize the ammonia,
thus eliminating it. However, the by-product of ammonia
oxidation is nitrite, which is also highly toxic to fish.
Nitrites levels as low as low as 1 mg/l can be lethal to some
fish. Nitrite usually begins rising by the end of the first
week after introducing fish.
Third stage:
In the last stage of the cycle, Nitrobacter bacteria convert
the nitrites into nitrates. Nitrates are not highly toxic to
fish in low to moderate levels. Routine partial water changes
will keep the nitrate levels within the safe range.
Established tanks should be tested for nitrates every few
months to ensure that levels are not becoming extremely high.
Now that you know what is
happening, what should you do? Simple steps such as testing
and changing the water will help you manage the nitrogen cycle
without losing your fish. |
