I've only seen it in rainbowfishes but some fish disease books have shown it
on other fishes. Goyder River Rainbowfishes in particular, seem to be
exceptionally prone to this discolouration. Steve Prycroft has a few
theories on this subject but is a bit hesitate to spell them out.
The only other thing I know that causes a similar symptom is Thyroid
Swelling generally due to lack of iodine in the diet. But this is usually
easily seen by the lifting or growth under the operculum.
I have had some Goyders live for a considerable time before they die (In
most cases I just dispose of them anyway) but others die fairly quickly. I
guess you really need to have them diagnosed by a Vet.
Adrian.
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Adrian R. Tappin
"Home of the Rainbowfish"
http://www.ecn.net.au/~atappin/home.htm
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