It is my conviction that there are several "ulcer" diseases in fish but the one we see mostly in Rainbowfish (and especially in Trifasciata types, and that includes "Herbies")
is due to a form of Mycobacteriosis, or in other words - Fish Tuberculosis. There are several species of Mycobacteria that may be involved and remember it can be transferred to human beings especially through minor injuries exposed to infected fish and ta
nks - hence the term "Fish Fancier's Finger". Probably because of our different body temperatures, metabolism, immune systems etc it rarely is anything more than a nuisance in human medicine. However in aquarium circumstances it is likely to be eventuall
y fatal.
I understand the infection is highly contagious and infected fish don';t usually show any signs until they are subjected to stresses such as overcroding, poor water control etc which then decreases their immuno-competence and allows the Bacteria to take o
ff. I also seem to recall that once an ulcer appears that that fish is actively shedding Mycobacteria into the tank and is likely to be infecting others in the tank. So unless there is a pressing reason to keep that particular fish it should be disposed o
f immediately and all the other inhabitants should be considered as suspect thenceforth.
Probably the fish handler should wear rubber gloves and they and the net should be sterilised ( not the wearer necessarily, although there may be some hoped for exceptions). NEVER tip diseased fish down the toilet!!!
Steve Pyecroft did his Ph.D. thesis on Piscine TB so would be a good source of up to date info. All of the so-called "cures" are (to me) mis-diagnoses or remissions, usually induced by instituting environmental changes in water quality, temperature, diet
etc which allow the immune system of the affected fish to regain control as long as the disease has not progressed too far.
BTW I think there is some evidence to suggest that TB may even be able to transferred
in fish eggs - perhaps Steve or some one else in the know can enlighten us.
Sorry to carry on - got carried away.
Bruce