White Spot
White spot disease is caused by a parasite called Ichthyophthirius multifiliis.
This disease is also called Ick or occasionally Ich or Ichy.
Symptoms
The fish has white spots on its skin. The spots
are about the size of a pinhead and the fish can look as if it has been
sprinkled with salt or sugar grains. The
parasite also attacks the gills of fish.
This is more difficult to see.
The gills may look more red than usual, but this is hard to see, and
excessively red gills can be caused by a number of things. The gill infection makes it more difficult
for the fish to absorb Oxygen from the water and infected fish can show signs
of being short of Oxygen like “gasping” at the surface, or apparently breathing
very fast. This shortage of Oxygen can
be caused by many things.
Sometimes
fish will swim down and try to rub their skin against objects. This is called “flashing” and can be caused
by any skin irritation.
Sometimes
fish show no obvious symptoms, but simply die.
If a fish dies you should take a very close look at all the fish in the
tank.
This is a
very common disease of fish. If it is caught early it is completely curable. The
parasite is present at low levels in most aquariums, often without causing any
trouble. Most fish have been exposed to
this parasite and have developed some immunity.
Those fish that have been raised in the complete absence of the parasite
will not have this acquired immunity and will be very vulnerable to infection.
The
statement that this parasite is present in most aquariums is often
misunderstood. Ichthyophthirius
Multifilis cannot lie dormant for long
periods. It survives by living on fish.
An aquarium might be empty of fish for a month. It would be free of the white spot parasite. Then
a fish was bought which was free of any visible disease and then
quarantined. This fish could be
introduced into the empty tank and develop white spot. The erroneous conclusion might be drawn that
either the empty tank had dormant white, or that the quarantine was not
correctly done.
What
would actually have happened would simply be that the fish had a white spot
infection without any symptoms. A
successful parasite does not make its host ill.
If the parasite wiped out all the fish in the aquarium, pond or lake it
was in, the parasite itself would also die.
In the wild the white spot parasite is apparently successful and most of
the time does not kill its host. In the
unnatural ecosystem of an aquarium it can easily get out of balance and kill
all the fish. This is not only fatal to the fish; it is also fatal to the
parasite.
The ideal
parasite is one that actually gives some advantage to its host. As far as I am aware, having the white spot
parasite is no advantage to fish, but other parasite/host relationships may
have developed into symbiotic ones where both organisms get an advantage.
Stress
If
something stresses the fish, their immune system often becomes less
effective. The same effect can be
observed with people. You are much more
likely to get both minor and major diseases when you are under stress.
There are
many things that can stress fish. One
very common one is simply being caught, put into a plastic bag and transported
to a new home. A common time for an
outbreak of White Spot is just after a new fish has been added. Some people incorrectly assume that the new
fish has introduced the parasite. They
may then go back to the shop they brought it from and see that the tank the
fish came from is perfectly all right.
Other
types of stress include changes in temperature, pH, dH or any other water parameter.
Life Cycle
Ichthyophthirius Multifilis is an obligate parasite. This
means that it can only live in the presence of fish. The actual visible white spots are the
feeding stage, called a trophont.
The trophont grows and then drops off the fish, falling to the bottom of
the tank and forms a cyst called a tomont.
Inside the tomont as many as 1000 tomites can form. The tomont opens and the tomites go into the
water.
The time it takes for Ichthyophthirius
Multifilis to complete its life cycle depends on the temperature of
the water. At 6 degrees C (43 degrees F)
is gets through its life cycle in about 55 days, while at 29 degrees C (84
degrees F) it completes its cycle in only about 4 days.
The tomites have to find a fish
quickly or they will die. At normal
tropical fish tank temperatures they only have about 2 days to find a fish to
infect.
Treatment
The trophont on the fish probably
cannot be successfully treated, although claims have been made of successful
treatments with salt baths. The tomonts
on the bottom of the tank are also hard to kill although they can be removed by
gravel washing. Keeping the tank clean
will help.
The only stage that is readily susceptible
to treatment is the free swimming tomite.
This can be killed by many things including ultraviolet light, salt and
many other chemicals.
There are many possible forms of
treatment. All the different ways of
killing off the parasite suffer from the problem that there are many strains of
this parasite and they vary in their susceptibility to the treatments. Here are a few of the ways of treating this
disease:
Medications
There are many commercial
treatments for white spot. They
generally use some combination of chemicals like Methylene Blue, Malachite
Green, Formaldehyde, Acriflavine etc. In
our own tanks the medication I prefer is Wardley Ickaway, but different people
will have their own preferences.
Note that these medications are
absorbed by activated carbon and if you have carbon filtration it will need to
be turned off. Most of the medications
are also destroyed by ultraviolet light, so ultraviolet sterilization will also
need to be turned off.
Tetras and other Characins,
scaleless fish like loaches and catfish as well as baby fish are more
susceptible to many of these medications, and they will need to be used a half
the normal rate. You can use the half
rate at double the normal frequency.
Heat
The life cycle of this parasite
is speeded up enormously by heat.
Increasing the temperature will make the chemical treatments work
faster, but will also mean that the infection will spread faster.
However, if the temperature is
raised enough the parasite cannot reproduce and the infection can be cured just
with heat. But some types of fish cannot
survive the temperature needed to destroy white spot. To break the life cycle of this parasite you
need to raise the temperature to about 30 degrees C (86 degrees F). To actually kill the parasite you need to
raise the temperature to about 32 degrees C (89.5 degrees F). This temperature would need to be maintained
for at least four days to have much chance of killing the parasite. Not all fish can survive this treatment, and
many that can will be badly stressed by it.
Increased aeration will be needed because Oxygen does not dissolve as
much in warm water, and the fish’s metabolism increases as the water warms up
so the need more Oxygen.
This method of treatment is
sometimes the method of choice if you are treating Labyrinth fish like Siamese
Fighting Fish, Gouramis or Paradise Fish. These fish can survive the temperatures needed
and can breath air as well as water.
Chlorine
Some people have reported success
in treating this disease by the careful use of chlorinated tap water. Personally I would not attempt this, and I
advise other people not to try. The
actual level of Chlorine in the water as it comes from the tap varies, not just
with the locality, but also with the day of the week and the season of the
year.
Apart from the difficulty of
getting the dose of Chlorine right there is the problem that some places, like
the Adelaide Hills where I live have Chloranimated water. This is deadly to fish and I would not risk
using the water without dechloranimating it.
Salt
Salt will kill the white spot parasite, but different strains have different tolerances. Many
strains of white spot will be killed by 3 grams per litre of salt, but to be
sure you will need to use 5 grams per litre.
This means that many common aquarium fish cannot
survive the level of salt needed to kill white spot. Generally this treatment method is unsuitable
for fish from places without much salt in the water like the rivers Amazon, Congo,
and Orinoco.
It can be used on the livebearers like Guppies,
Mollies, Platies and Swordtails. It can
also be used with some of the Australian fish like the Murray Cod, Silver Perch
and Callop, but not safely on the Rainbowfish.
Most aquarium plants will be killed by this level of
salt.
Ultraviolet
Radiation
Ultraviolet light will kill the free swimming tomite
stage of the parasite, but can only work on the tomites actually sucked through
the ultraviolet sterilizer. You are more
likely to get good results if the ultraviolet unit is more powerful than
usually recommended for your sized aquarium.
An ultraviolet filter will help to prevent white spot,
but cannot be relied on to cure it.
Disease Free
Fish
It is possible to breed fish in the complete absence
of the white spot parasite. This happens
with many of the live bearers bred in Malaysia. These fish are grown in water which is a
mixture of fresh water and sea water, sometimes having as much as half the salt
concentration of pure sea water. These
fish will never have been exposed to white spot and to some other diseases and
will be very susceptible to them. These
fish can be wiped out quickly. If they
are bought they need to be observed and treatment applied quickly as
needed. Aquarium shops will normally
warn their customers that the fish are disease free.
Secondary
Infections
White spot infection damages the skin of the fish and
it is common for bacterial or fungal infections to occur together with the
white spot.
Susceptible
Fish
Some types of fish get the white spot disease more
easily than others. The Clown Loach has
a particularly bad reputation for getting this disease.
