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| Filtration, Water Quality And Water
Testing |
Fishes live in very close contact with the water in their aquarium. They
continually absorb some substances from it into their bodies, while
excreting others out. Some of these waste products - such as fish
droppings - can be seen, but most are invisible. Polluted or poor
quality aquarium water is without any question the main cause of fish
health problems, and can also affect plant and algae growth. Thus caring
for an aquarium is mostly about caring for the water.
There are many different aspects of water that are relevant to aquarium
keeping - ammonia, pH, nitrite, etc, etc. It is essential to regularly
test the water in your aquarium, and a complete set of basic test kits
is available at Wayside for under £20. However, exactly what you need to
test for depends on the fishes you are keeping, the type of set-up you
have, and how long it has been running.
Water Testing When The Aquarium Is Running In - New Tank
Syndrome
Certain water quality problems are associated with new tanks. This is
due to the way that aquarium filters work. Filters do trap floating
particles, helping to keep the water looking clear, but this is not
their main action. The exact design varies, but all filters pump
aquarium water through something with a very large surface area -
usually sponges, gravel, or porous rock chippings. This large surface
area and continuous water flow enables the filter material to be
colonised by millions of bacteria. These bacteria play a vital role in
keeping the aquarium water pure. The problem with new tanks is that it
takes time - several weeks - for the filter to become full of these
bacteria. Until this happens, the filter cannot work properly, and will
not be able to keep the water pure.
The most important waste product that fishes produce is ammonia. Ammonia
is a simple chemical, composed of nitrogen and hydrogen, produced inside
fishes (and humans for that matter) when proteins are broken down to
release energy. Ammonia is very poisonous and must be eliminated from
the fish’s body, so it is excreted straight out into the water via the
gills. In the vast expanses of the fish’s wild habitat, the ammonia is
so diluted that it causes no problems, but in the confines of an
aquarium it will rapidly build up. When it breathes this polluted water,
the fish will then breathe the ammonia back in through its gills, and
poison itself.
Certain types of bacteria can ‘feed’ on ammonia, and as they do so they
remove it from the water. These bacteria will naturally start to
colonise the filter as soon as ammonia becomes present, and this is how
a filter purifies the water passing through it. As they feed on the
ammonia, these bacteria transform it into a different substance, called
nitrite. Unfortunately, nitrite is also poisonous, although less so than
ammonia. However, the nitrite can then be transformed by other bacteria
into something called nitrate, which is much less harmful. The important
point is that all these bacteria will take time to grow. Because of
this, in a brand new aquarium it is vital to add the fishes very slowly
over a period of months. A small number of fishes means a small amount
of ammonia in the water - not enough to poison anybody. When the filter
bacteria have increased in number enough to handle this level of
ammonia, a few more fishes can be added, and so on until the aquarium is
fully stocked.
Water testing is very important during this time. The amount of ammonia
fish produce can be unpredictable (it depends on diet, temperature and
the species concerned). Likewise, the speed at which the filter bacteria
will grow is difficult to judge. It is crucial to use an ammonia test
kit to keep an eye on levels of this in the water: if there is anything
more than a trace amount present the fishes will rapidly become ill or
even die. In the same way, levels of nitrite must also be monitored with
a test kit. An emergency partial water change can be done to dilute
levels of these substances if necessary. (It is also worth noting that
plants will remove some ammonia from water, as they use it as a
fertiliser). When levels of ammonia and nitrite reach zero and stay
there, the filter is coping with the number of fishes and, providing the
aquarium is not already fully stocked, more can be added. For this
reason, it is a good idea to test your water before buying any new
stock.
Some fish keepers with a new tank opt for so-called ‘fishless cycling’.
This refers to the practice of developing the filter bacteria in an
empty aquarium before actually adding any fishes. A source of ammonia
that does not come from fish waste is added to the aquarium for this
purpose. This may be pure ammonia (which can sometimes be bought from
chemists) or simply a piece of meat or fish bought from the supermarket
- as this rots in the tank ammonia will be naturally produced. Once
ammonia is in the water, the filter bacteria will feed on it and grow in
the normal way. This method has two advantages. Firstly, it is usually
quicker than simply adding the fishes gradually - if enough ammonia is
produced, the filter bacteria can be completely developed within six
weeks or so and the tank is ready to be fully stocked. (At this point,
of course, either the pure ammonia stops being added, or the rotting
material is removed). Secondly, this method avoids putting any strain on
the fishes: since ammonia levels can be unpredictable in a new aquarium
(as discussed above) the fishes may be at risk from water pollution
unless the tank is closely monitored. The only disadvantage of fishless
cycling is that it is impossible to know by looking when the aquarium
filter bacteria are fully developed, so constant water testing for
ammonia, nitrite and nitrate is required.
Although having insufficient filter bacteria and thus problems with
ammonia or nitrite levels is usually referred to as ‘New Tank Syndrome’
it is possible for it to occur in older aquariums as well. Anything that
causes the filter bacteria to die off in large numbers will effectively
wipe out the tank’s filtration capacity. Common causes are power cuts or
broken pumps (no flow through the filter so the bacteria in it start to
die); certain fish medications (some are toxic to filter bacteria);
leaving the tank empty of fishes for more than a few days (without the
fishes to produce ammonia, the filter bacteria have no source of food);
and washing the filter material under a tap (cold, chlorinated water
will kill off most of the bacteria). Always maintain your filter
according to the manufacturer’s instructions.
Water Testing And Water Changes In An Established
Aquarium
It is sensible to continue testing for ammonia and nitrite even in an
established aquarium (one that is more than six months old). Test about
once a week, or immediately if you notice any kind of problem with the
fishes’ health or behaviour. Also, because ammonia and nitrite
eventually turn into nitrate, this will need to be monitored as well,
with a nitrate testing kit. Nitrate is only harmful to fishes at
relatively high concentrations, but exactly how harmful depends on the
circumstances, so it is something to be aware of.
Along with nitrate, established aquariums can have other water quality
problems. The natural processes of the filter and the fishes’
metabolisms cause the pH to drop over time (usually making the water
more acid) and the phosphate levels to rise (encouraging the growth of
algae). In order to dilute nitrate or phosphate and maintain the pH, it
may be necessary to perform partial water changes on the aquarium.
This is when part of the water, usually about a quarter, is removed from
the aquarium and replaced with fresh water. This new water must
obviously be of the same composition as the usual aquarium water,
roughly the same temperature, and treated with a dechlorinator to remove
chlorine or chloramines. Water changes are generally performed once a
week or once a fortnight. A good way to establish whether a tank needs
more frequent changes than it is currently getting is to compare the
nitrate and pH readings with those of the water used to fill it (usually
the local tap water). If the aquarium water has a significantly lower pH
or higher nitrate reading than the tap water, more partial water changes
need to be done.
It is also possible to test for other factors, such as water hardness,
or dissolved oxygen. However, these are generally only relevant if the
fish keeper is adjusting the conditions of the aquarium water, or
keeping less common species. In this case, obtaining a basic book that
covers fish keeping and water quality in more depth is a very good idea.
Finally, remember the simplest water test of all: keep a thermometer
handy, as water temperature is something that also needs to be checked.
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