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Keep readings at an acceptable level
If the test kit readings show an elevated ammonia or nitrite level,
it is important that steps are taken to reduce it and bring it back to
an acceptable level. It should be pointed out that we are not aiming for
a zero level, as there has to be a low level of ammonia/ nitrite to
encourage the nitrifying bacteria.
Water changes
The simplest way to control ammonia / nitrite levels is to dilute the
build-up of toxins by carrying out partial water changes. The most
common problem is that the levels are allowed to build-up too high,
which means massive water changes are needed just to bring the levels
back to an acceptable level.
The aim should be little and often - usually changing between 10 -25%
of the water, depending on the test kit reading. For example, if the
reading is twice as high as the acceptable level, one would need to do a
50% change in order to bring the level back in line.
Stating the obvious, the higher the initial stocking level, the more
water changes will be needed to maintain an acceptable level. Which of
course is why fish should be gradually introduced to the new pond /
tank. The other influence is feeding. Feeding should be kept fairly
light during the first few weeks and certainly no more than the fish can
eat within 2-3 minutes, once or twice a day.
As the filter starts to mature, the need for water changes will
decrease.
Water changes
Ideally, when doing water changes the replacement water should be
treated with a de-chlorinator (available from an aquatic shop),
and preferably been left to stand for 24-hours. Whilst this is easy for
a tank, this can be difficult for a large pond as the water needs
to be treated with a de-chlorinator before
it is put in the pond. This why it is best to try and reduce ammonia
production (and subsequent nitrite production) by gradually increasing
stocking and feeding levels as the filter matures.
However, if ammonia / nitrite levels do reach a dangerous level, this
represents more of a risk to the fish than a water change with untreated
water. Such is the danger of elevated levels of these two toxins.
Other ways to assist
Elevated ammonia and subsequent nitrite levels can be reduced by
using zeolite in the filter system. This silicate rock removes ammonia
from the water. See the zeolite page
for more details on usage. This can be useful where there is a
particular problem - i.e. stocking levels too high with elevated ammonia
levels despite regular water changes.
Elevated nitrite levels can be assisted by adding salt to the water
at a rate of 3g / litre. However, this only helps by blocking nitrite
from entering the fish's blood and does nothing to prevent stress, skin
and gill damage. It can also be difficult to keep track of the salt
concentration if you are doing water changes. Salt is very useful
in assisting against raised nitrite levels - but it is important that it
is used in conjunction with water changing in order to keep nitrite
levels as low as possible.
Filter start-up products are available which claim to
"seed" the filter with suspended bacteria to speed up the
maturation process. I am not aware of any work carried out to verify
these claims - so it is a question of suck it and see!
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