Cotton wool disease (<i>Saprolegnia & Achyla</i>)


White - grey cottonwool tufts.
Whitish-grey cottonwool-like tufts grow on the skin.
White/grey threads on skin
Skin shows thread-like pieces flowing from it.
Faded colours
Colours of fish look washed out compared to normal.
Temperature sudden changes
Temperature has been changed suddenly usually downwards in recent days
Fins folded
The fins of the fish remain in a closed position due to discomfort.
Listless and lethargic
Fish moves very lazily in water, much less than normal, lacks interest.
pH water low <6.5
A few species of freshwater fish (Discus) can tolerate lower than 6.5 pH.  If lower than this and problems, suspect this a possible cause.
Reluctant to feed
Fish comes to eat but with evident lack of appetite.


True Fungal infections, almost invariably a secondary infection. Invades wounds caused by parasites, bacterial infections or mechanical trauma.


Very hard to treat, since the few effective substances (Malachite green) cannot be used for food fish.


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DNA and RNA diagnostic references

Multiple barcode assessment within the
Saprolegnia-Achlya clade  ( Saprolegniales, Oomycota, Straminipila) brings
order in a neglected group of pathogens. 

From  IMA Fungus Dec. 2014    Monica M. Steciow et al.


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