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Koi Pond
Water Quality (Page 2 of 3)
by Elmer Epistola
Posted: October 13, 2004
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I myself had been a victim of
NPS when I was starting out. At that time, I was mainly
concerned with the adequacy of oxygen supply in the pond. I
just switched from aquarium keeping to pond keeping, and never even
had the inkling that ponds are also filtered. I enjoyed
adding fish to the pond during the first week, only to be greeted by
a couple of dead fish one morning during the following week.
The next few days that followed were horrific - fish died daily
until I practically had nothing left. In panic, I bought books
about setting up ponds and immediately saw where I could have done
things differently. Novice hobbyists who are about to set up a
new pond must not take this phenomenon for granted.
At low levels (below 0.1
mg/liter), ammonia acts as a strong
irritant
to the koi, especially to its
gills. Flashing may be exhibited by koi irritated by low
levels of ammonia. Higher ammonia levels can lead to skin and gill
hyperplasia. Gill
hyperplasia refers to
the condition wherein the secondary gill lamellae become swollen,
resulting in breathing problems for the koi. Serious gill
disease and death can occur if the lethal levels of ammonia
contamination are reached.
The acceptable
ammonia reading
for koi ponds is, well,
zero.
Thus, your pond is threatened by ammonia as long as your test kits
are able to detect ammonia in your water.
Sooner or later, the rate of
ammonia level build-up in a new pond will decrease as biological
filtration does its job, but another toxic compound will be taking
over as this happens. Ammonia is converted by the nitrosomonas
bacteria into nitrites, which are also harmful to the fish, but not
as deadly as ammonia. Nitrite levels therefore shoot up as the
ammonia levels go down in a new pond.
Nitrites (NO2)
at low levels can subject the koi to stress, making it vulnerable to
diseases caused by other factors. High levels of nitrites
cause skin and gill epithelia damage, which can lead to parasitic
invasion or secondary bacterial infections. Fish suffering
from nitrite poisoning will be gasping at water surface and stay
around water outlets. Water testing kits must register
nitrite readings
of zero
as well if the water is to be considered nitrite-safe. Unsafe
nitrite readings can be corrected by sufficient partial water
change. Adding salt to the pond (around 0.02%) also makes nitrites
less toxic to koi, since their gills will tend to take up the added
chloride ions instead of the nitrite ions, getting protection from
the latter.
Figure 2. An electronic
device capable of
testing several water
parameters
Eventually nitrite readings in
a new pond will go down, just like the reduction of ammonia levels
before it. Again, the reason for this is the conversion of
nitrites into nitrates by 'good' bacteria, this time the nitrobacter
sp. Nitrates are significantly less toxic than nitrites, but
they should still be included in regular water quality checks.
Nitrates (NO3-)
are generally harmless to koi, although koi had been observed to
lose their appetite if the nitrate level is allowed to go unchecked.
Nitrate level should always be kept under
60 parts per million (ppm),
which is equivalent to 60 mg per liter, although some koi experts
say that a nitrate level of 100-500 ppm is not yet detrimental to
koi. Partial water change is a good remedy to
higher-than-normal nitrate level. The use of plants and
trickle filters will go a long way in stabilizing the nitrate level
of the pond.
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