great article on winter care
richdeer3pondsupplies.com
think all of us can learn new information from it.
Winter's Effect
On Koi, Goldfish, and Ponds
Presented By:
Richard E. Carlson
The purpose of this section is to describe the effects of cold
temperature on the ecology of the pond and its physical effects on the
fish. We as pond-keepers are required to prepare the pond and the fish
for a cold-water environment and more importantly, we must prepare the
fish to emerge from the cold in the spring.
When we consider the ecology of the pond, we look not only at the
quality of the water but also the effects of cold water on the
organisms within the ecology. Most notably, we need to focus on the
metabolic changes that the fish will experience as the water
temperature drops and what effect the change in water temperature has
on the naturally occurring nitrifying bacteria and parasites in the
pond.
Water Temperature Effects
One of the few things that we cannot effectively control in our pond's
ecology is the water temperature. The good news is that Mother Nature
has provided our fish with a natural ability to adapt to the colder
temperatures. This makes it our job to provide the best environment
possible and to duplicate what nature intended to happen in natural
waters. The bad news is that Nature has equally provided the other
organisms in our ponds the same survival mechanisms. Throughout this
section we are going to discuss not only the effects of water
temperature on our fish, but also on the nitrifying bacteria in our
filters, the algae and plants in our ponds, the parasites that live on
and around our fish, and finally on the disease-causing pathogenic
bacteria that also inhabit our ponds. Managing a pond into and out of
the cold weather season thus becomes a balancing act of nature and the
management of the entire ecology our ponds.
How cold does it get?
The first thing to consider when looking at water temperature effects
is to ask how cold our pond really gets. As pond owners, we should
know which temperature zone we live in and from this we can determine
the expected frost line depth in our soil. Local agriculture extension
services and most garden shops know this information, as do all
building inspectors. The importance of the frost line is that this is
the depth that the soil temperature will potentially reach 32 degrees
F. Below this depth, chances are that the soil temperature will remain
at 35 degrees F or above. Keep in mind that the soil around your pond
will act as a natural insulator and keep the water at the bottom of
the pond at a temperature above 35 degrees F. If you had the ability
to measure soil temperature at depths of twice the frost line, chances
are you find that the soil temperature does not drop below 40 degrees
or so, thus providing a nice natural insulator for our pond water.
Knowing the frost line depth should then be a major factor when
determining the depth of your new pond or whether or not your fish can
survive in your existing pond. As a general rule, the pond depth
should be at a minimum twice the depth of the frost line. For
instance, in Zone 7, the expected frost line depth is 12 inches, so
the minimum safe pond depth should be 24 inches below ground level.
But these rules only apply to ponds built into the ground and not for
ponds built above the ground. For above-ground ponds, the effects of
cold air are remarkably more drastic, and cause thicker ice coverings
and lower temperatures throughout the pond.
To understand how cold our ponds really can get, we need to use some
principles of both physics and meteorology. From physics, we first
need to understand that mass has everything to do with how our ponds
react to sub-freezing air temperatures. By mass, we are talking about
volume in terms of length, width and almost most importantly depth.
The greater the mass of the pond, the more assured we can be that the
natural cooling of our ponds will occur. Ice cubes in our freezer
freeze because they lack the mass to avoid freezing solid. Also from
physics, we know that as water cools it becomes denser and this dense
water sinks to the bottom. Water reaches its maximum density at 39
degrees F and this means that water as we know it, does not colder
than 39 deg F. Given a proper mass of our pond, we can expect the
entire pond to get no colder than 39 deg F. Although for ponds deeper
than four or five feet below the frost line, we may expect some
thermal layering (see below).
So, as the cold (below 35 deg F or so) air and soil temperatures cause
the pond water temperatures to lower, the denser cooler surface water
sinks to the bottom and eventually the entire pond will achieve the
same 39 deg F temperature. Since koi can withstand water temperatures
down to 35 deg F, this 39 deg F is a good temperature for our koi to
appreciate its winter surroundings (see torpor, below).
But with closed system ponds, such as most koi and goldfish ponds, we
routinely see water temperatures below this magical 39 deg F. This
happens primarily because the ground around the pond and above the
frost line is contributing to the cooling of the water. We can make an
analogy to the ice cubes in a freezer as the air surrounding the water
in the tray causes the water in the tray to freeze solid. The same
thing is happening to closed system koi ponds and the smaller the
pond, the worse the situation is likely to be.
But this begs the question: if water can only reach 39 degrees F, how
does it freeze? And here is where some principles of meteorology come
into play. First, let us understand what "ice" really is: ice is the
crystallization of water particles in the air. We can prove this
because we know that ice cubes float and ice bergs float. Freezing
water is a physics phenomenon as water expands and becomes less dense
as it freezes. Virtually everything else does the opposite. The
composition of ice is 10% less dense than water and so it floats.
Why does this happen?? As mentioned, ice is formed by the
crystallization of water particles but this freezing occurs ABOVE the
water line. During this process, air is trapped in the freezing
crystals and this causes increased mass but less density as air has
very little density. The meteorologists also tell us that evaporation
is always occurring above a body of water and with "calm" conditions,
the air layer directly above or ponds becomes saturated with water
making the humidity 100% directly over the water. Since we know that
ice is formed by crystallizing water particles, it is this layer of
humid air directly over the pond surface that freezes, not the water
surface itself. The depth of the ice is determined by the air
temperature at the ice surface interacting with the surface water
temperature. The colder the air, the lower temperature of the ice is
just above the water's surface. Between the surface of the water and
bottom of the ice is an air gap, where a continuous 100% humidity
level is maintained by the evaporation of the pond. It is the
interaction of the warmer pond water and colder ice that causes an
increase (or decrease) in ice depth.
The Effects of Salt on Water Temperature. As we are aware, salt is
used in many ponds for a variety of reasons and many pond owners still
use high levels of salt in the fall to help reduce parasite loads
going into winter. In fact, not too many years ago it was an
"accepted" practice to keep high levels of salt in the pond all winter
long to guard against parasites. We know now that this is a bad
practice as high levels of salt in the pond over winter can lead to
serious, if not deadly, problems for the fish. The chloride component
of salt (sodium chloride for table salt) affects the density level of
water and by doing so can effectively lower the physical temperature
of water. As stated earlier, the physics of water tells us that water
at natural "fresh water" levels cannot get below 39 Deg F under normal
conditions. We know that the natural chloride (or salt) levels of
fresh water are between .02 and .1% depending on location and source
water. At these levels, the temperature of water is not affected by
the presence of chloride. However, as we raise the level of chloride
above the natural levels, the density of water reaches its maximum
level at lower water temperatures. This effectively will allow the
water temperatures in the pond to drop below the 35-39 deg F range and
adversely affect the fish.
So, it is a good practice to recommend to those using salt to reduce
their salt levels to "natural" levels (below .1%) before winter sets
in.
Thermal Layering. There is often much discussion about thermal
layers in water especially when water movement (through pumping) is
considered. Thermal layers are distinct changes in water temperature
and density that can be registered at certain depths. In the summer,
the water is warmer at the surface and cooler as we get deeper due to
the effects of both the sun (warmer) and the insulating qualities of
the soil (cooler). Also, the cooler water is denser and will sink to
the bottom. In the winter, this effect remains the same even with the
colder water (caused by surface cooling) at the surface and the warmer
water at depth. During winter, the pond will constantly adjust itself
as the water warms from the sun and cools again at night. This effect
is transient and does not usually affect the overall condition of the
pond. But this explains why we might see our fish swimming at the
surface in the cold sunshine of winter.
Many ponders believe that water movement should not be permitted in
ponds during cold water times and especially a pump should not be
placed at the bottom of the pond as it will remove the "warmer" water
and cause the entire pond water temperature to drop below acceptable
levels. In fact, appreciable thermal layering does not occur in ponds
less than six feet deep and so in most ponds thermal layering is not
an issue and pumps and water movement can safely be done all year
long. However, to be on the safe side, it is advisable to place any
pump no more than mid-depth in the pond, as the real value to any
water movement is the more effective removal of gas build-up in the
water. Plus, if something goes wrong, the entire pond will not be
drained. As always, automatic pump shut-off switches are recommended.
In deeper ponds, 5-6 feet or deeper, the potential for thermal
layering, called thermoclines, exists. A thermocline is a weak
physical barrier caused by changes in water temperature at depth.
Under the thermocline is the warmer water and since this is also at
the bottom of the pond, this is where we can expect the fish to be
while in torpor. Since the thermocline is an effective, albeit weak
barrier, gasses such as CO2 and Hydrogen Sulfide can get trapped below
the barrier and create worse water quality conditions than above the
barrier. The net effect is that the fish are exposed to these trapped
gases and adversely affected. The simple way to eliminate the
potential for thermocline problems is to place a small pump on the
bottom of the pond to move the water gently thereby disrupting the
thermocline barrier.
Cold Water Effects on the Biological Nitrification Processes
One the issues often discussed in cold water keeping circles is what
really happens to the biological bacteria as the water gets colder.
To get the "right" answer, we can look to an industry that has
contributed much to the technology of koi keeping... the water waste
treatment industry. This industry brought us both the trickle tower
and bead filter technologies and has taught us much about the
nitrification processes under all conditions. Waste water treatment
plants use floating bed media for the biological treatment of nitrogen
products in waste water. These floating media beds remove ammonia,
nitrites, and nitrates from the water during the treatment process and
are the forerunner of our bead and floating media filters. But what
is really important is that these water treatment plants run all year
long! What this tells us is that the biological nitrification
processes continue even during the coldest water conditions. This is
an important fact to remember as those ponders who keep their filters
running all winter will retain a significant level of biological
nitrification processing throughout the winter and will see no
accumulation of ammonia or nitrites while the fish are "under the
ice."
Cold Water Ecology and Magic Numbers
As the water temperature at mid-depth of the pond begins to drop and
hold at lower readings, we need to pay special attention to what is
happening to the ecology of our ponds. The first magic number we need
to look for is 62 degrees F. At 62 degrees, the activity of the
nitrosomonas bacteria begins to reduce significantly. The effect of
this, of course, is a reduced ability for the filter system to manage
the conversion of ammonia to nitrites, which is the role of the
nitrosomonas bacteria. To offset this, we can reduce the amount of
high protein feed offered and mix our normal feed with a lower protein
or wheat germ food. The reduction of protein lowers the ammonia output
by the fish (see below).
Also at 62 degrees, we see a significant dip in the koi's immune
system's ability to fight off bacterial invasions. This is where your
fish start becoming increasingly vulnerable to ulcer and other
bacterial infections. If your fish are strong and you have cleaned
your pond well, you should not have problems.
The next important temperature mark is 55 degrees F. At 55 degrees,
the nitrifying bacteria in our filters begin to die off as well,
although they will not be completely gone until about 42 degrees F.
The effect of this is that our filters begin to loose the ability to
eliminate nitrites. Left unattended, we are creating significant water
quality problems. So, we need to take some definitive actions.
First, we need to change the diets of our fish to a food with lower
protein content. Normal summer-type koi feed has protein levels in the
range of 35-40% (or higher) depending on the type of food used. For
colder water feeding, we need to switch to a food with a lower protein
content, somewhere in the range of 30-32%. The reason? It is protein
content in food that is a major contributor to ammonia production by
the fish. By lowering the protein levels in the food, we thereby lower
the ammonia output. It is important to note that 65% of the ammonia
produced is not from feeding but a result of normal respiration. Thus
it is important to make sure we control the 35% that we can.
Below, and courtesy of the Hikari USA Company, I have posted the
protein levels and contents of three favorite koi foods. The first is
a high-growth food, normally fed only during summer months. Note the
protein level.
Hikari Hi-Growth
Koi With Championship Size & Form Can Be Yours!
Guaranteed Analysis: Crude Protein 42% Min. (Green)
Crude Protein 25% Min. (Yellow)
Crude Fat 8% Min. (Green)
Crude Fat 7% Min. (Yellow)
Crude Fiber 1.5% Max. (Both)
Moisture 10% Max. (Both)
Ash 12% Max. (Green)
Ash 7% Max. (Yellow
This food is a basic stable diet for koi and fed normally only during
warmer months as well. The fish will not grow as fast nor will the
filter system complain as much.
Hikari Staple
Preferred Daily Diet For Koi & Other Pond Fish
Guaranteed Analysis: Crude Protein 35% Min.
Crude Fat 3% Min.
Crude Fiber 5% Max.
Moisture 10% Max.
Ash 12% Max.
This type of food is a good cold-water food because of the reduced
protein levels and ease of digestability. Note the low protein levels.
Hikari Wheat-Germ
Easily-Digested Daily Diet For Koi & Other Pond Fish Providing
Outstanding Conditioning Of The Skin
Guaranteed Analysis: Crude Protein 30% Min.
Crude Fat 4% Min.
Crude Fiber 4% Max.
Moisture 10% Max.
Ash 12% Max.
Next, as the water temperatures drop into the 55-degree range, the
koi's metabolism begins to slow and its need for nutrition reduces as
well. This slowing of the koi's nutritional needs also allows us to
reduce the amount of food we provide to the fish. You will begin to
notice that the koi are less active, except during times when the sun
warms the pond and they begin to form groups at the bottom.
Occasionally the fish will graze on the algae growing on the sides and
bottom of the pond and seem quite content to do nothing more.
The charts below illustrate a correlation of water temperature, immune
system condition and nitrifying bacteria condition. This is a
compilation of accepted data from a number of published sources. In
the first chart, the effects of pond water temperature are shown
against the activity levels of the nitrifying bacteria (nitrosomonas
and nitrobacter) where the filter is not operational. Also note the
range where the koi's immune system is most effective. The increased
activity of the nitrifying bacteria increases the quality of the water
as harmful ammonia and nitrites are removed from the water. This
increase in water quality then supports the koi's ability to build and
maintain its immune system. It looks like Mother Nature knew what she
was doing when she developed this part of the ecosystem.
For many years, Cheerios was recommended if the owner had to feed the
fish something (guilt complex) and the reason for using Cheerios is
that it was very low (like zero) in protein. But as we have learned,
Cheerios is high in carbohydrates and as such, are not good for fish
in cold water conditions where they cannot burn off the carbohydrates
effectively. A lower protein fish food is a much better choice for
cold water feeding IF it must be done at all.
Another thing to consider regarding feeding is that owners should NOT
"pack it on" during the fall as the fish's natural storage and
processing systems provide for sufficient nutrition all winter long.
Keep in mind the fish are not in torpor and so their processing
nutrition requirements are minimal during cold water times.
At 50 degrees F, stop feeding your fish altogether. At this point the
fish's much lower metabolism will not allow proper processing of food
in the gut. Koi, unlike most animals, do not have stomachs and so all
food is processed in the gut. With a slower metabolism, the food moves
through the gut slower and the body's need for nutrients is reduced as
well, so the net effect is that the food is not processed properly. If
overfeeding during cold weather occurs, there is a real chance that
the food will spoil in the gut and cause significant damage to the
fish intestinal tract and quite possibly kill the fish.
And finally, at 40 degrees F, all nitrobacter activity ceases. This
makes your biological filters essentially useless and they should be
cleaned thoroughly and prepared for shutdown. When you actually
shutdown your pumps and filters is a call only you can make, but the
overriding concern is freezing of the plumbing and the loss of a pump,
filter, or worse yet - the draining of your pond from a ruptured water
line.
Cold Water Ammonia and Nitrites
Now that we understand what happens when pond water temperatures drop
to 50 degrees Fahrenheit and below, we are all too aware that our
biological filters have ceased to be effective against ammonia and
nitrite build-ups in our ponds. In fact, the fish are still producing
ammonia through respiration and what little food they are eating, so
it is a good practice to monitor ammonia and nitrite levels over the
winter months. So, let's look a little deeper at the effects of
ammonia and nitrite on our fish during the cold-water months.
First ammonia: in numerous articles and publications, we have read
that ammonia is much more toxic in high pH (alkaline) water and since
this is true, we must always balance our ammonia readings with the pH
readings of the water to get a better picture of the extent of the
effect on our fish. However, it is also very important to point out
that water temperature has a profound effect on the toxicity of
ammonia as well. In order to understand the effect of water
temperature and pH on the toxicity of ammonia, let's take a look at
how we need to interpret ammonia testing.
Most commercial kits for ammonia testing provide readings for what is
called Total Ammonia Nitrogen or TAN. If you read the labels and
instructions on your test kit, chances are you will see where the
manufacturer uses the term "NH3/NH4" as the "ammonia" the test kit is
capable of reading. The term "NH3/NH4" is Total Ammonia Nitrogen. So,
let's take apart this "Total Ammonia Nitrogen" and see what we are
actually dealing with.
Ammonia in water occurs in two different forms: Ionized Ammonia which
is represented as NH4 and Unionized Ammonia (UIA) which we see as NH3.
The combination of NH4 and NH3 are what is termed Total Ammonia
Nitrogen (TAN). The average ponder's test kit cannot differentiate
between NH4 and NH3 readings and so the TAN number is provided. But it
is the Unionized Ammonia (NH3) that is the only ammonia form that is
toxic to fish. And it is both water temperature and pH levels that
will determine which form of ammonia is predominant in the water at
any given time.
The toxicity of UIA begins at levels as low as 0.05 mg/l and so
determining the UIA level from inside a TAN reading can be a valuable
exercise for pond keepers. UIA levels of 2.0 mg/l are the levels where
fish begin to die off quickly. As stated, both water temperature and
pH levels impact the toxicity of UIA and so when TAN tests are
performed, it is important to read to both the water temperature and
pH levels as well in order to complete the picture. Below are a couple
of examples that illustrate the effects of water temperature and pH on
TAN readings:
In Table 1 below, the first example shows a TAN reading of 0.5mg/l
from the ammonia test kit. The water temperature is 50 degrees
Fahrenheit and the pH 8.0. The first reaction to getting a positive
ammonia reading is that the ammonia level is unacceptable and water
changes, chemical treatments, or other measures are necessary to bring
the ammonia under control. But a closer look at the actual situation
shows that the UIA, the toxic form of ammonia, is 0.0219 mg/l and in
fact under the 0.05 mg/l "undesirable" level and thus does not pose
much of a threat.
TAN
Water
Water
Factor *
UIA (NH3)
Level (mg/l)
Temp (F)
pH
Levels (mg/l)
0.5
50
7
0.0018
0.0009
0.5
72
7
0.0046
0.0023
0.5
86
7
0.008
0.004
0.5
50
8
0.0182
0.0091
0.5
72
8
0.0438
0.0219
0.5
86
8
0.0743
0.03715
0.5
50
8.6
0.0688
0.0344
0.5
72
8.6
0.1541
0.07705
0.5
86
8.6
0.2422
0.1211
Table 1
* The "FACTOR" column of the chart provides conversion factors
available from a number of sources, including the University of
Florida Cooperative Extension Service, Institute of Food and
Agricultural Sciences.
In reviewing the contents of Table 1, it is easy to see the
correlation between water temperature and pH and the toxicity of UIA.
For instance, compare the UIA level for a pH of 7 and a water
temperature of 86 (.004 mg/l) and the UIA level for a pH of 8.6 and a
water temperature of 86 (0.1211 mg/l). The effect of increased pH at a
constant water temperature and constant TAN reading yield dramatic
differences in UIA levels, with the increased pH resulting in greater
toxicity of the UIA. This is the basis of the argument that higher pH
readings make ammonia levels more toxic.
Next, compare the UIA level for a water temperature of 50 deg F. at a
pH reading of 8 (0.0091 mg/l) and the UIA level for a water
temperature of 86 deg F also at a pH of 8 (.03715). Here it is easy to
see the impact of water temperature on UIA levels with constant pH and
TAN readings with the cooler water offering more protection against
UIA toxicity.
Now nitrites: unlike ammonia, which has an immediate toxic effect on
fish, nitrite problems are caused by an accumulation of nitrites over
a period of time. Nitrites basically replace the O2 levels in the
blood thus causing "brown blood syndrome" and eventual death to the
fish through extreme O2 deprivation. So, it takes some time for koi to
accumulate enough nitrites to cause serious problems. How much time?
That depends on a number of critical factors including nitrite levels
in the water, the chloride levels of pond water, and the metabolism of
the fish. In colder water (50 deg F and under) we know that the fish's
metabolism slows significantly and one of the results is that he
respiration will be less. This results in a decreased opportunity to
take up nitrites from the water. However, lethal levels of nitrites
can still be accumulated over time if the nitrite problem is not
addressed.
For most ponders facing nitrite levels during cold water periods, salt
is the best treatment as salt levels of only .1% will inhibit the
uptake of nitrites and prevent brown-blood syndrome. And salt levels
of .1% can be maintained for indefinite periods of time without a risk
to the fish or concern for developing salt resistant parasites.
Water Quality
One of the major points we need to make to pond owners is to check
water quality over the winter months routinely as this can tell them
how the pond is doing and what needs to be done to head off or fix
problems. This should happen whether the filter is running or not.
Here are some key points to water quality in winter:
1. Expect levels of ammonia in the water. Even
though the fish are not eating, ammonia is being produced by
respiration and with no biological activity to speak of (unless the
filters are running), ammonia will accumulate. However, the cold
water makes it less toxic and almost harmless during the winter.
2. Expect low levels of nitrites. Low levels of
nitrites will not adversely affect the fish due to low uptake
potential. However, if there is concern, raising the salt level to .
08 to .1% will protect the fish and not affect the water temperature.
3. Test for KH levels routinely. Photosynthesis and
other biologic activity in the pond are depleting the KH levels
continually and as such, they will need to be replenished during the
winter months.
4. Test the pH often, getting both early morning and
late afternoon readings for comparison. The goal is hold the pH
stable at whatever level is natural for the pond (assuming the KH
levels are correct).
5. ORP readings can quickly tell us the overall
condition of the pond and from those readings we can react
accordingly, including water changes.
6. Do not be afraid to change water in the dead of
winter. Remember that significant evaporation has occurred
(especially if there is an ice layer) and the water levels need to be
replenished and refreshed. Add the water more slowly than usual to
allow for temperature changes and use dechlorinators as needed.
7. Significant thawing and heavy snow will have the
same effect on a pond as heavy rain. Typically, snow (like rain) is
acidic and can affect the pH of the pond unless the KH levels are
properly maintained.
8. Use a good in-water digital water thermometer to
keep track of the water temperatures at the bottom of the pond.
9. Aerate and circulate the water to help release the
gases in the pond and refresh the water.
Cold Koi
As stated above, Nature has provided our fish with the ability to
withstand cold water temperatures and you can expect your koi to
withstand water temperatures down to 35 degrees F. (Koi are primarily
bred in Niigata, Japan, where winters are long and harsh, and
snowfalls of over 20 feet are not unusual.) Of course, we are not
talking about rapid temperature changes but merely the "natural"
cooling of the water as the seasons change. As the water temperatures
decrease and stabilize at incrementally lower temperatures, the fish
experience metabolic changes where their body functions slow and
nutritional requirements decrease as well. (As with most health issues
for Koi, their immune systems can handle many water parameters - if
they do not change. Rapidly changing conditions are the enemy. This is
one reason why many suggest pond depths of 8 feet where the volume of
the water insulated by the soil will change very slowly, and allow the
Koi's immune system to keep up.)
At about 45 degrees F. you will see your koi start to become
increasingly lazy. In fact what is happening is that they are lapsing
into a condition called torpor. Webster's Dictionary defines torpor as
a condition of mental or physical inactivity or insensibility;
lethargy or apathy. Many animals hibernate during winter, which is an
almost complete shutdown of the body's systems. Torpor is different in
that it is not hibernation but a reduction of metabolism and related
supporting body functions to the point where the fish is lethargic.
Unlike hibernation, torpor allows the fish to understand its
surroundings and still be able to react to threats. So, while there is
mental activity, there is little physical activity. You may see your
fish grazing around the bottom during this time but it is not a
serious search for food.
It is also important to make sure that the Koi are not startled or
stressed, as they almost completely lose their ability to manage
stress situations. Koi do not have a "fight or flight" capability that
allows most animals to manage increased adrenalin build up. Instead,
koi will always flee a stress-producing situation and they do so with
a great burst of speed. In order for the fish to burst away from a bad
situation, they have a unique capability of producing great quantities
of adrenalin and epinephrine hormones into the muscle. This is why
fish can go from zero to warp-speed in a quick sudden burst. But what
fish do not have is the ability to easily remove that hormonal build
up. The net result is that fish maintain a higher level of adrenalin
and epinephrine too long, and this results in an increased need for
metabolic support and reduction of immune capability. So, it is easy
to see that with a reduced metabolic capability, a sudden and dramatic
increase in adrenalin build-up without proper release forces the fish
into great stress. This high level of stress can actually kill fish in
very short order.
Parasites, Bacteria, and Cold Water.
The next sets of organisms we need to discuss in the pond's ecology
are micro- and macro-organisms, more notably known as the parasites
and the bacteria. Here we will differentiate between the nitrifying
bacteria discussed above and the pathogenic bacteria that cause
disease in our fish. Both of these bacteria types are aerobic bacteria
which simply means that they need oxygen to survive. Most parasites
are basically warm-water creatures and as the water temperatures dip
into the very low 50's and high 40's, the common micro- and macro-
parasites begin to die off in great numbers. However, it is always a
good idea to do a .3% (3000 ppm) salt or, if you are an advanced
ponder - a potassium permanganate treatment, to your pond at about 60
degrees in an effort to reduce or kill off the lingering parasite
colonies. More about medicinal pond treatments is provided later.
The lone exception to parasitic cold-water intolerance is costia.
Costia, which is formally named ichthyobodo necator and not to be
confused with common "ich", is one of the smallest ectoparasites
(lives on the outside) and is especially active in water down to about
38 degrees F. This is what makes it so dangerous to our fish during
cold-water times. As the fish's immune system and metabolic processes
are reduced due to decreasing temperatures, costia parasites are still
active and have the potential to cause significant damage through
normal parasite attacks (cold water ulcers) and increased stress on
the fish. The good news is that costia is easily managed through salt
and/or potassium permanganate treatments.
But the real problem we face as koi keepers is how to reduce the
effects of aeromonas and pseudomonas bacteria on our fish during cold-
water times. Aeromonas (and I will lump pseudomonas bacteria into this
discussion as well) are the pathogenic bacteria that are the primary
cause of ulcer disease, fin rot, and mouth rot. There is significant
truth to the statement that aeromonas bacteria are ever-present in our
ponds and they really only get to effect our fish when the fish become
stressed or lack the ability to fight them off. Think of it this way:
- cold germs are ever-present in our surroundings and we become
significantly more susceptible to catching a cold when our resistance
is low, such as when we are cold or tired.
Consider the chart below. The activity levels of aeromonas and the
koi's immune system are compared. Note that aeromonas becomes active
at about 42 degrees (F) and remain active well above 90 degrees (F).
Now notice the koi immunity system activity. The fish only begin to
have the ability to fight off infection at about 45 degrees (F) or so
and by that time, the aeromonas are off and running at greater than 60
percent lead.
But the real problem area we need to consider is that portion of time/
temperature that we call Aeromonas Alley, where the net effect of the
aeromonas activity is so great and the koi's immune system so weak
that the potential for real trouble exists. Aeromonas Alley is the
pond water temperature range between 40 degrees (F) and 62 degrees (F)
and this represents the time where our fish are in most danger from
aeromonas infections.
To counteract the potential for disaster, especially while
temperatures are in Aeromonas Alley, ponders can take a number of
steps to reduce aeromonas loads, including the following:
Reduce the amount of organics in the pond with a thorough cleaning of
the pond bottom and filters. Remember that bacteria thrive in high
organic environments.
If possible, treat the pond with therapeutic potassium permanganate
treatments. PP removes the organic load through oxidation and also
kills off significant, if not all, bacteria in the pond. A therapeutic
dose of PP is 2PPM for 4-8 hours)
Add salt to your pond at a dose rate of no less than .2 % (that is two
pounds per 100 gallons) and keep it there for at least two weeks. Then
reduce the salt level to about .08 to .1% through water changes and
salt at that level for the remainder of the winter. This will reduce
the parasite load as well provide much needed chloride levels into the
water.
Reduce feeding of the fish. The primary food source of aeromonas
bacteria is fish feces. Actually, the slime coat on the feces. Reduced
feeding causes less feces and so less food source for the aeromonas.
There are a number of other tricks for protecting koi such as feeding
them immune system enhancing food, but the one that seems to work the
best is the use of Lymnozyme or Koizyme. It is rare that I will
specifically recommend any one product, but this is one product that
every koi owner should use. Lymnozyme is a natural enzyme developed to
help eliminate aeromonas bacteria by out-competing them for their
primary food source. In effect, the presence of Lymnozyme starves out
the aeromonas and reduces their numbers.
Below is an excerpt from a post I made on the AKCA web board. The
question was related to the use of Lymnozyme on fish already infected
with an aeromonas bacteria infection:
First, every pond has aeromonas bacteria.. it is a fact of life. They
typically only become a problem when the fish are stressed or weakened
by something else. Consider them opportunistic, if you will, as they
are looking for open wounds caused by injury or parasites, flukes,
etc. Lymnozyme reduces the number of aeromonas bacteria by exclusion,
in that it competes with the food source of the aeromonas, which is an
element of the fish's feces. Lymnozyme stays in effect for about four
days in your pond, so you can see that its addition reduces the
aeromonas count quickly. The most opportune time to use it is when you
suspect that your fish are stressed by bad water, parasites, flukes,
etc. and susceptible to infection. It is recommended to use it
extensively in the early spring and late fall when the fish's immune
system is easily compromised.
If you are using Lymnozyme now, then your problem is not necessarily
the standing aeromonas in the pond. Because you have an active case of
fin rot and this is mostly caused by aeromonas, the problem is that
the aeromonas on the fish have a food sources (tissue) as opposed to
competing for food in the water. This is why Lymnozyme does not work
on already infected fish. So, you need to treat the fin rot as an
infection and quite possibly systemic. Topical antibiotics, such as PP
paste or iodine, will help but if the infection is getting into the
tissue of the body, then you need to move to injectable medications to
stop it.
Lymnozyme is effective down to about 45 degrees F.
Hypothermia
Like all living creatures, koi and goldfish can suffer from
hypothermia. Hypothermia occurs when the core body temperature becomes
so cold that normal body functions begin to fail. In human beings,
this temperature is about 93 deg F. For koi, this temperature depends
on basically two things: how cold the water gets and how fast the
water gets cold. Koi are poikilothermic, which means that their body
temperatures are essentially the same as the water temperatures. And
because of this, koi have no ability to regulate their body
temperatures. As the water temperatures drop, so does the koi's body
temperature and this affects the fish's immune system and physiology.
So it is pretty easy to see why water temperature in a koi environment
is so critical.
Hypothermia can become a factor when the pond water drops below 39
degrees and really is a problem when it approaches 35 deg F or lower.
While all fish are susceptible to hypothermia, most fish do just fine
under normal cooling conditions, but there are some fish who just
cannot handle the cold. First evidence of hypothermia in fish is a
loss in color followed by rapid breathing/gill movement. Additionally
erratic swimming may occur that looks like that the fish is
disoriented. The affects of hypothermia can lead to hypoxia, which
basically means that the fish is starving for oxygen. While it is true
that cold water holds more oxygen by its nature, because the fish's
metabolism is so slow it cannot adequately take up oxygen and suffers
from low oxygen affects. Hypoxia can then lead to anemia and this puts
the fish in a serious position. Reversing the conditions of
hypothermia requires that the fish be removed to a tank that can be
warmed slowly.
Snow, Ice and Photosynthesis
Once our fish have settled in for the winter and the pond ices over,
owners tend to unintentionally forget about their friends under the
ice. Actually most of us don't want to think about them because we
think they are suffering. And while we know they really are not
suffering, what we do not know is what is happening under the ice.
So, let's consider what happens under the ice: if there is a heavy
layer of snow on the ice, certainly this will restrict the
photosynthesis processes and an abundance of CO2 and consumption of O2
will occur. Additionally, the algae, which need sunlight, will die off
and this will up the ammonia levels and reduce the O2 levels as well.
So, collectively a number of bad things are occurring, including the
reduction of the carbonate (KH) levels.
If there is significant algae in the pond, a common pond feature,
there is a photosynthesis process that contributes to the O2 levels in
the water. As you know, during daylight hours, plants through photo-
synthesis produce O2 (by consuming CO2) in the water and during the
nighttime, the process reverses and CO2 is produced (by consuming O2).
In ponds with grossly unbalanced ecosystems (plants vs. animals)...
the consumption of O2 becomes a real problem and will kill the fish.
For those of us who have seen it, we can confirm that it happens very
early in the morning and starts with the larger fish.
Oddly enough, the same process exists on very cloudy days and becomes
a real problem when we have a number of cloudy days in a row. The lack
of sunlight inhibits the photo-synthesis process and everything in the
pond thinks it is nighttime and so all of the O2 is being eaten up and
CO2 levels become dangerous. The simple solution of course is
increased aeration.
Now, the problem with CO2 is that is it highly acidic and will dump
the pH to hazardous levels quickly. So you get a combination of low O2
(suffocating) and a high acid (low pH) environment. This causes
acidosis in fish that no amount of Tums or Zantac will help.
You can confirm all of this by a couple of quick tests. First, check
the pH early in the morning and if it is on the low end of the scale
or unacceptably acid, then there is the makings of a CO2 problem.
Next, check the KH. The same thing if it is too low. Low KH also
causes an additional problem in preventing pH swings. Always watch the
fish. If they are near the surface, either near the air hole or near
the ice, then chances are that they are piping and looking for O2 and
not getting warm or watching the TV. This is an indication that low O2
exists in the bottom of the pond. And finally, monitor ammonia levels
always, just in case...
The simple remedy for all of this is aerating the pond in the winter.
Some ponds will do just fine with an air hole while others, especially
those with good algae growths, may need an air stone or pump breaking
the surface.
One more test if you are wondering about the ecosystem of the pond....
if there is some open water, fire up a pump and splash it for 48 hours
and see if foam (DOC) appears on the surface. If it does, then the
pond has a high organic load and evidence that potentially you may
have a low O2/high CO2 problem. In some ponds, you may also get foam
forming around the air hole heater. This is not a casual coincidence,
but evidence that you have the potential for problems. Using an ORP
meter routinely throughout the winter can give an excellent indication
of the water's condition.
As you can see, the ponds ecology continues even though the fish have
gone into a state of torpor and it appears all is calm in the pond.
Some hints for helping the pond and fish out during the winter months:
1. Test the water routinely, especially for ammonia, pH, and KH
levels. This will tell you almost everything you need to know about
what is happening under the ice.
2. Remove snow from the pond's surface as soon as possible. This
will permit sunlight to filter through and positively affect the
photosynthesis processes.
3. Keep a hole in the ice open at all times. This will permit the
escape of gases (mostly CO2) from the pond water and allow the pond to
breathe. This is an essential step.
4. If practical, keep an air stone or a small pump running just
so there is some water movement. This will assist in the agitation of
the water and the release of gases such as CO2. If a pump is used,
make sure that a hydrostatic shut-off switch is used also or place the
pump high enough in the water so that it will not drain the pond if
something goes wrong.
5. Keep supplies of Amquel/Prime, baking soda, and salt on hand
just in case you need them to help Nature along just a bit.
Cold Water First Aid
No matter how hard we try to keep things perfect, too often something
goes wrong and our fish need some first aid. In the late fall and very
early spring we are likely to see aeromonas infections (ulcers, mouth
and fin rot) as this pathogenic bacteria has the upper hand in the
cold pond. Also, we are likely to see fish under great stress from the
cold water and a parasite load or internal bacteria infection.
Indicators of this are when the fish assumes a laying-over position
and will appear dead on the bottom until disturbed. At this point, the
fish may right itself and swim normally for a while only to resume the
laying-over position. While this laying over posture can occur under
hypothermic conditions as well, chances are greater that the problem
is a bacterial infection. In any event, treatment starts with a very
slow warming of the fish.
So, when we see these types of problems, we need to perform a little
first aid to help our fish along. But there are some tricks to
treating fish in cold water/weather environments.
Try to keep the fish in the same temperature water to which he is
acclimated. Many well-meaning fish owners will put the fish in warmer
water thinking this will help, when in fact this will most likely kill
the fish. Koi can only handle a temperature change of 10 degrees at a
time. Plus, fish "know" their water and by keeping them in water they
know will reduce some of the stress. A good trick is to perform pond-
side treatments with a quick release back to the pond.
If the decision is to bring the fish indoors, plan on keeping him
inside until spring. Too many ecological changes will do more harm
than good. When the fish is brought inside, use pond water in the
largest container you can handle and let the water warm "naturally"
until it hits room temperature. The longer it takes to warm, the
better. A little ice can help to slow down the process - monitor the
water temperature and allow no more than a 1 degree temperature change
per hour, and no more than 5 degrees in 12 hours.
If the fish needs to be netted, do so as gently as possible. Netting
adds to the stress of the fish coupled with cold water and parasites/
infections, only compounds the problem. Pond-side salt dips for
parasites (.6% for 30 minutes or less) should be done using pond water
in a large container and with some effort at reducing the effects of
the cold air.
If the fish requires injectable medications, consult your veterinarian
on which anti-bacterial agent has the best uptake in cold water (I am
willing to bet it is Baytril - although the effectiveness of any drug
is somewhat area-dependent, and high levels of resistance have been
cropping up for Baytril). Perform the injections pond side and release
the fish. But keep an eye on it closely as possible. Curing bacterial
infections is a tricky business in warm water, let alone in cold water
where the fish has no immune system to speak of. If you are
experiencing ulcers or tissue rot, your only course of action may be
to bring the fish indoors for the Holidays.
Cold Water Bloating
One of the more common problems we see in cold water settings is a
bloating of the fish, including bulging eyes and raised scales.
Normally these symptoms are associated with dropsy, the clinical
presentation of fluid accumulation in the body cavity. With dropsy, it
is usually a bacterial or viral infection or a parasitic attack on one
of the internal organs that causes the fish's body to react with
increased body fluid production. However, there is another cause of
bloating that will offer the same symptoms but is a much less sinister
problem. As was mentioned earlier, the metabolism of the fish slows
considerably as the water temperature decreases and one of the results
of this process is an adverse effect on the osmotic regulation system.
Once the osmotic regulation system gets out of balance, the fish loses
an effective way to regulate its body fluids and the result is a
retention of excessive body fluids. Thus we get classic bloating. I
have found this common in ponds where there is a fluctuation of water
temperatures in the colder ranges (35 to 50 deg F) or that temperature
range where the fish is moving in and out of torpor.
The treatment for this type of bloating is fairly simple, however the
procedures for maintaining the fish post-treatment can get tricky. A
bloated fish needs to be removed to a separate tank with water the
same temperature as the pond's water. It is best to use pond water for
this treatment not only for its temperature but also to reduce stress
on the fish. I use a 100 gallon Rubbermaid trough as the q-tank. The q-
tank is placed in the garage (unheated) and fitted with a small pump,
a 300 W heater, and a grow-light on a timer (with on-off the same as
the sunset-sunrise). I then wrap the tank with R19 house insulation
and put a cover on the tank (but not sealed). Let the water warm
slowly with the heater and at the same time, bring the salt levels up
to .3%. The water temperature you finally achieve will of course
depend on many factors but anything above 52 degrees and holding
steady is good. The combination of warmer water and increased salt
levels should jump-start the osmotic regulation system.
I have seen bloating reduce within 48 hours and the fish start
responding to the warmer environment by looking for food. If the fish
does not respond within 48 hours and a noticeable reduction in
bloating is not realized, up the salt level to .4%. You can repeat
this every 48 hours up to .6% without significantly stressing the
fish.
The drawback to this regimen is what to do now with a warm fish in the
middle of winter. This is a tough call and must be considered before
removing a fish for treatment under winter's conditions. Obviously the
fish would be reasonably content to stay in the warm tank but this may
not be convenient. So, what you need to do is reverse the procedures
for getting the fish to this point by reducing the water temperatures
slowly until they equate to the pond's temperature. More than likely
you had to change the water in the q-tank and so it is a good idea to
now use pond water to replace any tank water lost to water changes.
Also reduce the temperature settings on the heater. If you are lucky
you can catch a warm spell where the pond's temperatures may have
risen a few degrees. If not, once the tank temperatures and the pond's
temperatures are within 5 degrees of each other, it is time to return
the fish to the pond.
One critical thing to consider when adjusting q-tank water
temperatures is that the water temperatures in the tank may vary
greatly during the night as the outside temperatures drop. This is why
we should use as large a tank as possible to do this procedure as
increased water volumes are less susceptible to temperature changes.
And finally, the same q-tank procedures can be used for any fish in
distress that may need to be temporarily removed from the pond for
treatment.
Filter Cleaning
One of the really important parts of maintaining a healthy winter
environment and ultimately a successful spring start-up, is proper
cleaning of the pond's filter systems. If you have bead-type filters
or filters systems that collect solids from the pond, you need to take
special precautions to make sure that they are cleaned properly. In
the beginning of this chapter we referred to the pathogenic and
nitrification bacteria as aerobic bacteria, or bacteria that needs
oxygen to survive. There is a second type of bacteria, called
anaerobic bacteria, which also requires mentioning. Anaerobic bacteria
does not require oxygen to thrive and as such lives in some of the
more distasteful environments, such as in heavy mulm on pond bottoms
or the accumulated crud in filters. Left alone, this mulm and crud
will become havens for anaerobic bacteria and it presence is
potentially very harmful to our fish. One of the most common effects
of anaerobic bacteria build up is hydrogen sulfide, an extremely
deadly compound that has killed more than its share of fish.
In all too many cases, filter systems are not properly cleaned and
shut down during winter and when they are re-started in the spring,
great clouds of anaerobic bacteria are released into the pond much to
the detriment of the fish. Also, bottom crud (mulm), including sludge
and decaying plants and leaves, will produce large quantities of
anaerobic bacteria and hydrogen sulfide gas that when disturbed later
will poison the pond and its inhabitants.
The best bet is to take a little extra time in the late fall to
thoroughly clean and shut-down your filter systems and clean the
bottom of the pond. One of the tricks that your fish may enjoy is to
swirl around the bottom stones and rocks and mix up the crud on the
bottom just before your last filter cleaning. Not only will this get
the crud into the water so it can be filtered out but will also
release many tasty morsels for your fish to enjoy as a final snack.
Filters can be taken off line and bleached to kill off any unwanted
bacteria. If you bleach filters in the fall, the chlorine should not
be harmful when you start up the pond again in the spring.
Many pond owners, especially with bead filters, are finding ways to
keep them running all winter long as means of achieving a fast start
in the spring. This can be an excellent practice so long as the
filter is protected from freezing. The most exposed area of a bead
filter is the bottom sludge drain as these tend to freeze and break
open first. A simple trick to protect the filter is to place a 60W
light bulb (on a GFCI circuit) at the base of the filter near the
sludge drain and then wrap the entire filter base with fireproof
household insulation.
And finally, at the first falling of the leaves, cover your pond with
a net. This simple act will save you and your fish much time and
trouble. Make sure that you remove all leaves and debris that get into
the pond as often as possible. Clean any power skimmers that are in
use at least every 24 hours.
Conclusion
I have a consistent theme to all of my pond endeavors and that is to
duplicate Mother Nature whenever possible. In natural waters, the
water supply is replenished by springs and rivers and the fish are
treated continually to refreshed water. In our ponds, we have to
perform this natural act routinely to ensure the environment and
ecology stay clean and balanced. This is why we perform water changes
and test the water quality often and why we leave a hole in the ice
when our ponds freeze over. This is our best attempt at duplicating
what Nature would provide.
There are no magic tricks to keeping our fish alive and healthy during
the winter months. There are some common sense efforts that we can do
to make sure that what Nature does well and naturally, we do
ourselves. Cleaning the pond and preparing our fish with the right
food and environment are basic to keeping them healthy. If we do this
and work with Mother Nature, our fish will emerge in spring looking
healthy, hungry, and much to our surprise - larger than when they went
under the ice.
Places for on-line help:
Affiliated Koi Clubs of America (AKCA): www.akca.org
Dr Eric Johnson (DVM): www.koivet.com
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