Author: Dr. L.E. Freese
Three
of the most common diseases that affect fish are fin-rot, Ich and
fungus.
FIN-ROT
Fin-rot is the progressive
erosion of the tissue between the fin rays caused by opportunistic
bacteria. The erosion begins with the reddening of the fins followed by
the fraying and erosion of the fin membrane. At this stage it is common
for secondary fungal or bacterial infections to occur.
Fin-rot
is treated by firstly eliminating any environmental aggravators such as adverse
water conditions, stress and aggressive or incompatible tank mates,
which leads to injury.
The affected fish can be treated with a bath
immersion of salt (salt tolerant fish) or treated topically with gentian
violet. Otherwise if more than one fish is affected they may be treated
with a proprietary medication.
ICH (WHITESPOT)
Ich is caused by parasitic
protozoa called Ichthyophthirius
and is highly contagious. The white spots, commonly found on the fins
and body of the fish, are the diagnostic sign, but the spots can also be
found on the gills and eyes.
The best way to prevent Ich from being transmitted to
your tank is to quarantine new fish and plants before adding them to the
aquarium. Generally the fish’s immune system is strong enough to fight
the disease but in stress conditions, the immune system is hampered and
the parasite has the upper hand. Poor water conditions, bad diet or
overcrowding can contribute to the spread of the disease.
Ich can be treated easily and effectively and deaths
are not common if the fish are treated in the early stages of the
disease. Treatment should start by the removal of environmental stresses
and then the tank should be treated for 10 to 14 days with the
appropriate medication as the life cycle of the parasite is of this
duration.
COTTON WOOL
DISEASE / FUNGUS
Cotton wool disease is a general term used for
external fungal infections, which are characterized by fluffy, whitish,
cotton wool like growths. (A bacterial infection commonly called mouth
fungus is also known as cotton wool disease.) Untreated fungal
infections attract dirt and algae growths that change the growth to a
gray or reddish brown colour in the later stages of the disease. If the
fungus is not treated the growth will spread and ultimately be the cause
of death. As fungus is highly infectious the disease spreads rapidly
from one fish to the other.
The fungal spores
that cause cotton wool disease are found in most aquariums and the
fungus can be seen feeding on organic matter in the aquarium such as
left over food and fish carcasses.
The best way to
avoid the prevalence of cotton wool disease is to minimize stress and
remove other predisposing factors such as poor aquarium hygiene,
chilling, injury and other diseases.
Cotton wool
disease is treated either by a salt bath immersion (if salt tolerant),
topical application of gentian violet or by the appropriate fungicidal
medication.
These
diseases are highly infectious and by the time that the symptoms appear,
other fish are also affected. The affected fish are normally treated in
a hospital tank due to the fact that most medications destroy the
nitrifying bacteria in the filtration systems. The problem with this is
that the fish tend to be placed under extreme conditions of stress and
they are most often too weak to overcome the additional netting wounds
and stress. It is therefore important that the main tank is treated, the
nitrifying bacteria remain unaffected and that the affected fish be
treated correctly.
June 2001
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