There are two main types of fungus. The "True Fungus" and
the "False Fungus".
The false fungus is called Mouth Fungus, Mouth Rot, or Columnaris
Disease. While this disease shows all the signs of being a fungus it
is actually a bacterial infection.
Small, off-white to grey, marks on the head, but sometimes on the fins
and gills. The lips are most likely to be infected, and the inside of
The initial lesions develop into off-white fluffy growths resembling
cotton wool, hence the confusion with true fungal infection. Mouth fungus
has however a coarser and more granular appearance, and is often greyer
in colour than true fungus.
A systemic infection, usually occurring at tropical temperatures, with
an incubation period of a few days. Fish do not always show external
symptoms but may die in just a few days. Diagnosis is normally only
possible on a post-mortem examination. This disease may be responsible
for some unexplained deaths.
Cause - Flexibacter Columnaris
The bacterium is commonly present in aquariums water, on dead organic
material, or even on healthy fish skin, and may invade damaged or unhealthy
skin and the surrounding tissues. The bacterium appears to be more pathogenic
under hard water conditions with a pH above 6.
Good husbandry. Don't keep fish under the wrong conditions, i.e. Fish
from hard or alkaline waters in soft acid water.
Monitor your aquarium for correct pH, Nitrite, Nitrate, and Ammonia
levels. Ill health due to incorrect environment is far more likely than
than flexibacter infection.
Bath immersion using a treatment containing Phenoxyethanol is normally
effective. It is also fungicidal and will cater for misdiagnosis in
case of true fungal infection.
The true fungus or cotton wool disease.
Fluffy, usually white or whiteish growths, and usually at the site of
an injury or where the skin has been damaged by disease, including wounds
left by large parasites or by fighting. Untreated fungal growths may
turn grey to reddish-brown with time, as they accumulate dirt and algae.
The untreated areas will soon spread to healthy tissue which will eventually
lead to death. Fungus is often seen as a secondary infection to diseases
like fin rot.
A number of different types of fungus including Saprolegnia are commonly
blamed for all fungus and Achyla. Other fungi may be involved and a
single site may be attacked by many species of fungi.
Fungi are found in most aquariums feeding on dead and decaying plant
and fish matter. In fact anywhere the water quality is poor.
Good husbandry cannot be stresses enough. Stress, poor hygiene, chilling,
injury, old age and other diseases will allow fungal infections to multiply.
Do not dose the tank, if it is not really needed.
If only one or two fish are infected, a hospital tank is the better
option. If all or most of the fish have fungus, you will have to treat
the whole tank but this will be useless if you do not solve the underlying
problem (see prevention).
The following options are available.
A prolonged salt bath has an effect on most fungi and is better for
the fish and plants as long as they are salt resistant.
Add an aquarium fungicide, one containing Phenoxyethanol can be used.
If you have no room for a hospital tank and the fish is still fairly
healthy you can apply the fungicide directly on the affected spot with
a soft swab. This minimizes stress to the fish as it is returned to
it's own tank straight away.
Don't Forget good hygiene, minimal stress and proper feeding should
help give no problems of this nature.