This has been called many things: fungus,
protozoan, parasite, fish pox and more. A lot has been written about it and
no one is any the wisher. The problem is that there has been no research done,
as it does very little harm.
One thing I do agree with though, is that
frogs do carry it.
It looks very like fish/carp pox - a cyst forming
organism which builds up and bursts. However, unlike fish/carp pox it's not a
solid lump, it's whitish yes, but looks as though it's full of tiny white
spheres and has a pinky appearance.
This kills quite a few koi, mainly
in spring or autumn when the water is quite cool. It's often thought to be
white spot and so formalin and malacite is poured into the pond and it's this
treatment that kills the fish, not dermocystidium.
There very little
more I can say other than try to learn to identify it and be able to
distinguish it from fish/carp pox. How it ever gets mixed up with white spot
simply amazes me!
Dermocystidium is mainly seen on fish's fins. It can
be found on fresh and marine fish, often underneath the fish near the vent and
If it's removed from a fish, and just dispatched and
prepared for microscope slide the spore count is unbelievable.
true form it can be mistaken for papillomas tumours, but not a fish disease.
Research is under way, but the finding may never be known unless it
affects the value of game fish.