Unlike paying taxes, testing our ponds is entirely voluntary, so let's
consider three good reasons for volunteering. First, knowledge is power.
Second, prevention is easier (and cheaper) than cure. Third, learning can
be fun. The reasons for not testing - too time consuming, too confusing,
too expensive,and just not necessary - don't stand up in light of the facts,
as we shall see. Another consideration is that we generally have koi ponds
for two basic reasons - the beauty of the water environment and the pleasure
of having koi. Water testing goes to the heart of both these issues - keeping
the pond attractive for our enjoyment and keeping the water healthy for
our fish. The latter is the most important reason to test, for, as hardy
as koi are, long-term exposure to poor water quality will cause stress
and disease. Unfortunately, we can not rely on our unaided senses to determine
water quality - clear water is not an indication of good water quality
from a fish's perspective.
Millions of years of evolution have resulted in fish that are superbly
adaptedto their natural environment. An attempt to create and maintain
an artificial pond environment for even domesticated fish is complicated
by the fact that fish are essentially "bags of water living in water"
with only a semipermiable membrane to maintain internal integrity.
Terrestrial animals such as ourselves, on the other hand, can be considered
"bags of water living in air" with enhanced barriers that, relative
to fish, effectively separate and protect us from our environment. We can
tolerate pollution and environmental changes much better than fish can
because our bodies do not interact with the environment as intimately as
do fish bodies. Fish are truly a part of their environment and are strongly
and directly affected by its condition.
Because koi are so adapted to and affected by their environment, it is
important that natural, healthy conditions be maintained in a pond to ensure
healthy, happy, colorful fish. Fish disease issues invariably involve water
quality. Poor quality stresses the fish, which in turn causes their immune
system to go down, which in turn makes fish susceptible to disease pathogens.
In order to know if there is good water quality, it only makes sense to
test it periodically rather than wait for disease symptoms to appear.
As a colleague, Barbara Johnson, The Fish Lady, says, "A pond is basically
a toilet." Fish waste must not be allowed to accumulate in a pond,which
usually means a biological filter must be operating properly. Fishwaste
and other organic debris are the first step in the nitrogen cycle, a series
of events that produces some of compounds we test for - ammonia, nitrite
and nitrate. Algae, or "nature's filter" as I call it, may colonize
and detoxify a pond with high levels of nitrogen compounds, but algae's
presence changes water quality for two other things we shouldtest for -
pH and dissolved oxygen. The last naturally occurring factors we routinely
check are temperature and water hardness.
When to Test
Individual, one-time tests are important if the test results indicate
a toxic or dangerous condition, such as high ammonia, and corrective action
has to be taken immediately. The greatest benefit of testing, however,
is obtained when results are plotted on graph paper over a period of several
testings, so that trends or directions can be noted early. By knowing the
direction your pond's water quality is taking, you can take corrective
action before the problem gets out of hand, as, for instance, with a major
Normally, tests for ammonia, nitrite, nitrate, pH and temperature should
be made once every week or two. Tests should be made more frequently during
periods of change in the pond, such as spring warming, new filter installation,
major pond cleaning or repair. At such times daily testing for certain
items may be necessary, for example pH tests for new cement work, chlorine
or chloramine tests for major water changes and ammonia and nitrite tests
for new filters. During stable periods such as mild summers, testing may
be cut back to once every three weeks, and during periods of midwinter
inactivity,testing can be eliminated.
Home kits all work the same way - there's a small container for a measured
sample of pond water, a chemical to add to the sample that will cause the
water to turn a certain color, a color chart to compare the result to and
instructions to tell you if things are okay or not. Some kits, such as
Tetra, use drops and some, such as Kordon and Aquarium Pharmacuticals,
use tablets - drops are faster and tablets are easier to measure. Test
kits come in either "master packs" which contain several basic
tests, or single test packs. Refills for the chemicals only are also available.
The chemicals of some kits have expiration dates, after which they don't
work properly, so watch for that. The basic tests are usually ammonia,
nitrite, nitrate and pH. Single test packs usually run from about $6.00
to $12.00, depending on the test and the brand and are good for 10 to 50
Following is a discussion on the specific factors tested for in a koi pond.
You do not need this information in order to properly test your pond, as
the commercial test kits are simple and easy to understand. Read this only
if you care to understand the factors behind the test results. Don't worry
about the technical measurements, because the color charts in the test
kits really make things very simple. There's no reason, for instance, to
convert mg/liter (which test kits measure) to oz/gallon because only the
ratio matters- and you don't even need that to read a color chart. What
is important to realize, however, is the interrelationship of various factors
in the pond. Also, results may vary depending on the time of day and how
long thewater sample was stored before being tested.
What to Test
Ammonia - introduced by fish waste and decomposing organic debris,
is themost toxic nitrogen compound, and is present in two forms in the
pond, free and ionized. Free ammonia is the most toxic and will cause death
in very low concentrations (0.15 ppm or 0.15 mg/liter). Problems associated
with non-lethal elevated levels of ammonia include gill disease, dropsy
and finrot. The higher the pH and the temperature, and the lower the salinity
or hardness, the greater the ratio of free ammonia to the ionized form.
Thus, the higher the pH and/or the temperature, the more toxic the ammonia.
Test kits measure the total (free plus ionized) ammonia, and the
following table, adapted from Tetra Press, The Manual of Fish Health, compares
pH, temperature and the maxium safe level of total ammonia, measured in
Maximum Safe Level of Total Ammonia - Mg/L
||41 degrees F
||50 degrees F
||59 degrees F
||68 degrees F
||77 degrees F
With a properly functioning biological filter, ammonia level is, in fact,usually
zero in a pond, and should at least be under 0.1 mg/l. The Nitrosomonas
bacteria in the filter oxidize ammonia into nitrite, our next compound.
If the ammonia level is elevated, you should immediately add ammonia remover
such as Tetra Aquasafe NH/Cl Formula, Kordon AmQuel, or Aqua 5 Chlora Gone
or make a partial water change ( a third to a half). You should also add
nitrifying bacteria, such as Aqua5, to your filter and stop feeding your
fish until the situation is corrected.
Nitrate is less toxic than ammonia, but still very toxic as it inhibits
the ability of the blood to carry oxygen. Nitrite is oxidized into nitrateby
Nitrobacter bacteria living in the filter, but some of the commerically
prepared bacteria compounds for ponds are rather skimpy in the amount of
Nitrobacter present because it is relatively expensive. Thus, your pond
may experience a nitrite spike as your filter is being conditioneduntil
the Nitrobacter colony reaches sufficient size to deal withall the nitrite.
If the nitrite level is elevated, i.e., over 0.1 mg/l, according to your
test results, you should make a partial water change andadd bacteria high
in Nitrobacter , such as Aqua 5.
Nitrate is the end product of the nifrifying phase of the nitrogen cycle,is
much less toxic for koi than either ammonia or nitrite. It is, however,
a nitrogen compound and is food and fertilizer for algae. In nature, nitrate
is absorbed by water plants and is reduced into free nitrogen by anaerobic
bacteria living in the bottom silt. Hydrogen sulfide and methane gas (the
noxious swamp odors) are given off as a by-product of the anaerobic process,
and most pond owners don't want anaerobic filtration. An oxygenated, clean
pond will not have any anaerobic bacteria present, so nitrate will accumulate
in the pond. An algicide is often used to control algae that would be attractedto
the nitrate, and partical water changes of one tenth a week or one third
a month are made to flush out the accumulating nitrate. If the nitrate
levelis over 20 mg/l, you should make a partial water change or add Aqua5
Dry, which contains bacteria that remove nitrate without producing hydrogen
sulfide and methane gas.
pH indicates the ratio of hydrogen ions (acidic) to hydroxyl ions (alkaline)
on a logarithmic scale from 0 (pure acid) to 14 (pure alkaline). Pure water
is 7.0, meaning that there is an equal balance of hydrogen ions and hydroxyl
ions. Most tap water is around 7.4 to 7.6, which is perfect for koi, as
they do best in water 7.2 to 8.0. Koi can actually tolerate a wide range
of pH, from 6.5 to 9.0, but they cannot tolerate a rapid change - more
than 0.2 per hour. (Note: the logarithmic scale means that there are 10
times as many hydroxyl ions at 8.0 as at 7.0.)
As mentioned above, pH affects the free ammonia/ionized ammonia ratio,
with a higher pH resulting in a greater concentration of the more toxic
free ammonia. To make things more complicated, algae and other water plants
can drastically change a pond's pH from night to day, due to a change in
the amount of dissolved carbon dioxide present in the water. We're concerned
about rapid pH shifts not only because of the ammonia ratio, but also because
the fish are trying to keep their blood pH even during these shifts, thereby
Carbon dioxide mixes with water to form mild carbonic acid; therefore,
more carbon dioxide means a lower pH, and less carbon dioxide means a higher
pH. A bloom of algae will take up a lot of carbon dioxide during daylight
for photosynthesis (causing pH to be highest in late afternoon), and emit
a lot at night through respiration (causing pH to be lowest in early morning).
Buffers such as bicarbonate ions help to keep the amount of carbon dioxide,
and therefore pH, even in the pond, but if there's too much algae for the
available carbon dioxide, it will be obtained from the bicarbonate ions
in the water, thus reducing the buffering agent and increasing the risk
of rapid pH changes.
Finally, even though koi can tolerate extremes of pH, there are diseases
directly caused by pH extremes, in addition to diseases caused indirectly
by the stress. Acidosis is a reaction of fish to acidic conditions, in
which they act highly agitated, with a lot of jumping. A rapid lowering
of pH will cause quick death, while a slow lowering below tolerance levels
will cause few behavioral changes until the inevitable death. In alkalosis,
a reaction to conditions that are too alkaline, the gills and fins are
destroyed; otherwise the symtoms are similar to acidosis.
High pH can be caused by improperly cured or sealed concrete ponds or mortarwork.
New concrete ponds should be sealed with penetrating water-based or epoxy
compounds, which not only provide a water seal, but also bond with the
lime to eliminate pH problems. Cement-based water seals don't do anything
to control pH.
For temporarily raising or lowering pH, you should use, respectively, sodium
bicarbonate and sodium monophosphate. If fish are in the pond be sure to
alter pH gradually - no more than a 0.2 change per hour. If an algae bloom
is causing pH shifts or extremes, you have to first determine if your filter
is working properly, in which case it's safe to kill the algae (while monotoring
dissolved oxygen levels). If an improperly operating filter is the cause
of the algae bloom, you have to first ensure safe levels of ammonia and
nitrite before it's safe to control the algae. Remember, go slow in fixing
a problem that probably took a long time to develop. Finally, if algae
are present, take an early morning and a late afternoon reading before
taking any corrective action.
Temperature is often viewed by pond owners as a guide to feeding more
than as a health issue for koi, should be monitored for both daily swings
and seasonal extremes. Temperature affects dissolved oxygen levels, respiration,
metabolic rate, pH balance, free ammonia/ionized ammonia ratio and osmoregulation.
Koi can tolerate a broad range of temperatures, from ponds that are iced
over to water up to 90 degrees, better than they can tolerate sudden shifts
in temperature. If you have a shallow pond (less than two feet deep) in
full summer sun along with cool summer nights, the pond temperature maybe
changing by more than four degees an hour, causing stress to the fish.
Greater splashing of the water and shading may control the problem. If
yourpond is subject to stressful temperature changes, a 0.1% solution of
sea salt containing calcium, potassium, sodium and trace elements will
reduce the stress as it aids the kois' osmoregulation. As with pH, do not
drastically alter a ponds' temperature by, for instance, adding ice in
the summer - do it slowly. Fish can tolerate a low to high change better
than they can a high to low.
Water hardness consists of two elements, permanent or general hardness
andtemporary or carbonate/bicarbonate hardness. Koi do better in hard water
because of the relation of salt within their bodies to the dissolved salts
in the pond. In soft water, the difference in salt concentrations means
the koi have to work harder, through the process of osmoregulation, to
prevent the salts within their bodies from diffusing out thorough their
Harder water allows the koi to ease up on osmoregulation and therefore
reduces stress. As mentioned above, bicarbonate ions buffer the water,
reducing pH shifts, another cause of stress in koi. Koi do well in carbonate
hardness of 150-300 mg/liter or 9-18 degrees dH. In most koi ponds the
water is too soft due to the fact that there is no natural mud bottom that
leaches minerals into the water.
Marine salt and sodium bicarbonate increase hardness, and will also cause
pH to go up. A permanent salt solutionof 0.1% is beneficial to koi, and
works out to about eight pounds per 1,000 gallons. Check your pH if you
add salt, and do not use table salt - the salt used to make salt water
aquariums is the best. Salt will not evaporate out, and needs to be replaced
only if water is drained from the pond.
Dissolved oxygen is usually only a warm weather concern, as it is associated
with water temperature and algae. However, the larger the fish, the greater
its oxygen demand - low oxygen levels will stress and kill your biggest
fish. Ponds that have been safe may become unsafe as your fish grow larger.
The colder the water, the greater its capacity to hold dissolved oxygen.
Algae take up oxygen at night, and an algae bloom can cause suffocation
in large fish and inhibit the oxidation process of nitrifying bacteria.
Also, dying algae and decaying organic material take up oxygen.
Testing for dissolved oxygen allows you to determine if your pond has the
maximum amount for the temperature of the water. Splashing the water into
small droplets with a fountain or waterfalls is best for aeration, although
venturi valves on underwater jets and air compressors also do a good job
Chlorine and Chloramine
Chlorine and Chloramine should be tested for if your water supply is
from any source other than your own well. Chlorine will burn off by itself
in a day or so, but chloramine must be broken down and removed chemically.
Check with your local water agency to determine whether they add chlorine
or chloramine. These chemicals damage the gills and liver, and even in
low concentrations can cause stress that ultimately leads to disease. Also,
frequently overlooked is the fact that they are added to the water supply
to kill bacteria. The beneficial, nitrifying bacteria in your biological
can be killed off by chlorine or chloramine in concentrations that do no
obvious damage to your fish. Good products on the market to eliminate chlorine
and chloramine include Tetra AquaSafe, Kordon AmQuel, and Aqua 5 Chlora-Gone.
Copper should be tested for if water is supplied to the pond via copper
pipes or if coins are thrown in the pond. Copper, in its most toxic free
form, will leach into softer water more readily than into hard water. It
damages skin and gills and c