Know
your water enemy
The conversion of ammonia to nitrate is actually a two
step process carried out by two different classes of bacteria. The first stage
is the oxidation of ammonia (NH3) into nitrite (NO2-) by nitrosifying bacteria
including species of Nitrosomonas, nitrosococcus, and Nitrosospira.
The second
stage is the oxidation of nitrate to nitrate (NO3-̊ , in this case by
nitrifying bacteria, primarily species of Nitrospira rather than the
Nitrobacter species often mentioned in older aquarium books.
These bacteria use ammonia and nitrite as a source of
energy, oxidising them to release energy the bacteria use to synthesise their
food. It is essentially a similar process to photosynthesis, where plants use
light energy to synthesise food, except in this case the bacteria are using
chemical “fuel” instead of sunlight.
New tank syndrome occurs whenever the filter is not
yet fully colonised by sufficient nitrosifying and nitrifying bacteria to deal
with the waste produced by the fish in the tank. It isn’t exclusively a problem
with new tanks, despite the name. every time you add new fish to a tank, the
tanks enter another period of new tank syndrome while the filter bacteria
multiply up to deal with increased amounts of fish waste.
Cleaning the filter
media too harshly or careless use of anti-microbial medications will knock back
the populations of bacteria as well, setting your aquarium up for another round
of new tank syndrome.
The
symptoms
Fish react to new tank syndrome in remarkably
consistent ways. Initially, they adopt stress colouration, and behave nervously
without showing much interest in food. Air-breathing fish such as gouramis and
cordoras make frequent trips to the surface to gulp air, while other will exhibit
signs of laboured breathing, such as gasping at the surface or very rapid
ventilation of the gills. Cichlids often dart about frantically, while bards
tend to adopt odd swimming postures.
If conditions remain poor, the fish start to lose
condition rapidly, becoming subject to opportunistic infections such as
whitespot, finrot, and fungus. Eventually, the fish die from ammonia or nitrite
poisoning. For inexperienced aquarists unaware of the early warning signs, it
is usually the sudden death pf most of their fishes that finally sounds the
alarm that something isn’t quite right…
Stage
one: the ammonia spike
When brand new aquarium is set up, it passes through
three distinct stages. The first of these is a rise and fall in the
concentration of ammonia, known as the ammonia spike. Ammonia is extremely
toxic to fish, with as little as 0.5mg/L being potentially deadly to many
species. Once the nitrosifying bacteria get established, the ammonia
concentration declines quite rapidly, and often this particular part of the
cycling process will be finished within a couple of weeks, at which point the
ammonia concentration in the aquarium should be zero.
Stage
two: the nitrite spike
A few days after the ammonia concentration has started
to decline you should begin to notice a rapid rise in nitrite concentration.
This nitrite is of course what the nitrifying bacteria need, and so this is the
part of the cycling process where they begin to get established in the filter.
Nitrite is marginally less toxic to fish than ammonia, with the critical danger
level being around 1.0mg/L. The nitrite spike usually reaches a peak around
three to four weeks after the aquarium is set up, after which point the nitrite
levels quickly drops down to zero, indicating that the nitrifying bacteria have
fully colonised filter.
Stage
three : rising nitrate
After about six weeks ammonia and nitrite levels
should be zero, and this means that the aquarium has reached the third stage in
the cycle, where the filter is fully matured and the only waste product the
aquarist has worry about is nitrate isn’t particularly toxic, and levels of 50
to 100mg/L are usually safe for most standard community tropicals.
Regular
water changes are usually enough to dilute the nitrite, keeping the ambient
levels low enough for most fish to thrive. However, a few freshwater species are
sufficiently intolerant of nitrite that the concentration will need to be kept
below 20mg/L. rift valley cichlids and discus are among the best known of these
nitrate-intolerant fishes, but mollies kept in freshwater rather than brackish
tanks seem to be similarly sensitive.
Quick
fixes
So what do you do if your aquarium is suffering from
new tank syndrome and your fish are starting to look unhappy. The first thing
to do is a water change. A 50% water change will make a huge difference, and
performed daily this can get you through the first dangerous weeks of fish
keeping without suffering any fatalities.
The filter bacteria will not be
inconvenienced by this, and the idea that they need high levels of ammonia and
nitrite to get establish is erroneous. So, along with your nitrite and ammonia
test kits, buy a big bottle of dechlorinator and be ready with your bucket and
hosepipe to perform large-scale water changes every day.
It is also important to only use hardy fishes while
cycling an aquarium. Goldfish and danios work well in freshwater tanks, and
black mollies do the job nicely in brackish water tanks. Hardy barbs, such as
rosy bards, also work well. Although guppies have often been recommended for
cycling tanks in the past, the rather delicate fancy guppies offered for sale
are not really up to this job, though wild-caught guppies (if you can find
them) may well be. Particular fishes to avoid are loaches, cichlids, and
oddballs such as pufferfish.
One way to jump-start a filter is to seed it with filter
media taken from another aquarium. A mature filter (at least six month old) can
stand to lose up to 50% of its filter media without major problems. Put the
media taken from that filter into the new filter, and hey presto, the cycling
process is almost entirely leapfrogged. Of course, this does rather depend on
not killing the bacteria while moving them from one filter to the other. Treat
the bacteria as you would fish: do not expose them to the air, and don’t
subject them to large changes in water chemistry or temperature either.
Another way to jump start a filter os to use products
such as Tetra SafeStart and Marineland BioSpira. These products contain
cultures of bacteria said to colonise a new filter so quickly that fish can be
safely introduced at once. While this sounds almost too good to be true, many
aquarists have used them with great success. That said, it would still be wise
to perform regular ammonia and nitrite tests for a few weeks after using them,
and of course carry out water changes as required.
Fishless
cycling
When setting up a tank, the temptation is to add too
many fish at once, and this often leads to deaths as some of the fish fail to
put up with the ambient levels of ammonia and nitrite. Even if you use just a
few hardy species, those fish are still being subjected to some pretty nasty
water conditions, and if you don’t want danios or goldfish, what do you do with
them after you’ve finished cycling the tank? In recent years fishless cycling
has become increasingly favoured as the more humane and flexible approach.
Traditionally, this was done by throwing in bits of
meat or seafood and just letting nature take its course. As this stuff decayed,
it produced ammonia, and that drove the colonisation of the filter by the
bacteria. The more modern approach is to add daily doses of ammonia bought from
a pharmacy or chemical supplier. Ammonia is of course highly toxic, and should
be kept away from pets and children. The exact amount will need to be worked
out by trial an error; add some to the aquarium, measure the concentration with
an ammonia test kit, and then either add more ammonia or dilute with
de-chlorinated water as required. Once you’ve worked out the amount you need to
raise the concentration of ammonia in the aquarium to one to five-mg/L, make a
note of this and add a similar dose every day. Each day or two, test with your
ammonia and nitrite test kits. With luck, you should see the ammonia level
peaking first and then the nitrite level, until eventually both settle down to
zero indicating that the cycling process has reached completing.
New tank
syndrome is one of those things every aquarist has to deal with. Fortunately,
it isn’t that difficult to manage properly, and by using fishless cycling or
jump-starting the filter it can even be side-stepped entirely.
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