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Koi Pond
Water Quality (Page 3 of 3)
by Elmer Epistola
Posted: October 13, 2004
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A
weekly
test for ammonia and nitrate levels is recommended, although this
frequency may be diminished if the pond has matured enough and
stable readings are already being taken consistently. Nitrate
level testing can be done only once a month. Of course,
any change
in the filtration system or koi pond itself necessitates a more
frequent regular monitoring once more until the readings stabilize
again.
Copper
and
iron
are examples of metals that are toxic to koi. Be sure that
your pond water is not exposed to these metals. Possible
sources of copper and iron are your piping system, heaters, and even
your filters.
Koi pond
water pH
is another water quality parameter that needs to be checked
regularly. The term 'pH' stands for 'pondus hydrogenii', and
is a measure for how acidic or basic your pond water is. A pH
of 7 means that the water is neutral. As the water becomes
more acidic, the pH number goes down. The pH number goes up as
the water becomes more basic. Koi pond water pH must be
maintained between 7
and 8.5.
Off-scale pH readings can
result in direct physical damage to the skin, gills, and eyes of the
koi. Prolonged exposure to incorrect pH can lead to stress and in
extreme cases, epithelial hyperplasia (swelling of the gills) or
even death.
Figure 3. An
off-the-shelf pH Test Kit
Water hardness,
on the other hand, measures the mineral (calcium, magnesium, iron,
zinc, etc.) content of the water.
These minerals are usually brought into the pond by rainwater that
has percolated through rocks. There are two hardness numbers
usually monitored in koi ponds, i.e., the KH (for carbonate
hardness) and the GH (for general hardness).
The pond's KH level (also known
as the alkalinity) determines its pH buffering capability, or the
ability of a pond to keep itself from becoming too acidic. The
pH of a pond is affected by a lot of things (such as plant
photosynthesis and the production of acids during nitrification),
and can swing in value from time to time. One way to stabilize
the pH of a pond is by neutralizing any acids introduced into the
pond with carbonate and bicarbonate ions, a process known as
buffering.
GH is just the sum of KH and
another hardness parameter, the permanent hardness. In a koi
pond, the permanent hardness is negligible compared to the KH, so GH
and KH may be treated as one for practical purposes.
In most water systems, water
hardness (GH or KH) is quantified in terms of the amount of calcium carbonate
(CaCO3) in the water (mg per
liter or ppm). Very hard water contains greater than 300 mg of
calcium carbonate per liter of water while soft water contains less
than 75 mg per liter. Koi ponds, according to koi experts, should have a water hardness
of 100-150 mg CaCO3 per liter of
water, or 100-150 ppm.
Soft pond water should be avoided because it forces the
koi to exert more effort in osmoregulation, the process of
maintaining internal body water concentration to the correct level.
Furthermore, a low KH results in pH instability, which can be lethal
in extreme cases of pH swing. On the other hand, mineral deposits will form in the pond if the
hardness exceeds 150 ppm. Note that some koi experts advise higher
hardness levels than this (even up to 300 mg), if only to assist the
fish in osmoregulation.
Water to us is but something to
drink, take a bath with, or swim in. To our koi, however, it
is what they breathe and live in, what dictates their bodily
functions and, ultimately, what determines whether they will live or
die. Indeed, koi pond water quality is something that every
koi enthusiast must never take for granted.
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