Re: Mycobacteria

[Rjga at aol_com]

I would add that in general, Mycobacteria are not very infectious, and the 
fish most likely to come down with it are old fish. The immune system 
deteriorates with age, and that's why they are the first to show it, even 
though it may be in the environment. Once you leave it untreated, then the 
infected fish eventually produces a large number of the microbes. Because 
they are not very infectious, small doses seldom affect healthy fish in the 
same tank, but large doses can overwhelm even healthy immune systems and 
bingo, you have an outbreak. This is the reason to immediately dump any fish 
that MIGHT have mycobacteria, and that includes old fish that have surface 
gray lesions or are skinny and wasting (even though they might have something 
else - don't take chances). 

Consider also that even if the fish has something else, just the fact of its 
being old means it is too weak immunologically to resist other microbes, so 
it will probably succumb to something else anyway. Just killing off the 
microbes or flagellates or whatever with medicaments won't solve the problem. 
If the immune system is weakened, then wiping out one microbe will only open 
the fish to infection with something else not affected by that particular 
medicament (such as a Gram positive opportunist taking advantage after a Gram 
negative microbe is killed by an antibiotic that only targets Gram negative 
microbes).

Bottom line is this. Watch your fish and at the first sign of something 
wrong, remove the questionable fish to isolation (if not the trash can) and 
do a water change on the tank, with a healthy dose of chlorinated tap water 
(perhaps 20% tap water that has not been dechlorinated). This reduced 
chlorine exposure will probably be well tolerated by the fish, but go a long 
way in reducing the microbial population in the tank.

I can't promise it won't kill your fish (don't know what kind of chlorination 
your town uses or the final dose at your tap), but it's a rule of thumb 
that's worked for me.

    

Robert J. Goldstein, Ph.D.
Robert J. Goldstein & Associates, Inc.
Environmental Consultants
8480 Garvey Drive
Raleigh, NC 27616 USA
tel  (919) 872-1174
fax (919) 872-9214
URL   www.rjgaCarolina.com
e-mail  rgoldstein at rjgaCarolina_com


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