I found that ulcers occur nearly exclusively in fish when conditions change. That is not necessarily a
change to the worse but may be a few degrees of temperature more for fishes which have been kept rather
cool. This makes it clear that it should be caused by any kind of weakness bacteria - but doesn't tell which.
There seems to be a chance to save the fish by treating them with certain antibiotics. However, every
treatment with antibiotics is a risc to human! I will explain. Anybody in this recent discussion already
wrote (sorry I forgot who :-( )that the use of erythromycin nearly caused his life because he is very sensitive
and gets an allergic reaction. This is the worst reaction but not the only one.
Using antibiotics in aquarism effects resistent bacteria which will develop according to the high degree of
possible mutations in bacteria. In human medicine we have the great problem that since a few years a
tuberculosis - thought to be no problem any longer - causes more and more deaths as doctors partially can't
find antibiotics which are still working against the bacteria. I don't know if there is a real danger coming
from an Aeromonas infection to men, but I know that there is a certain chance to become infected with fish
tuberculosis. At least one person in Germany already died on fish tuberculosis.
If a fish keeper gets fish tuberculosis antibiotics which have been used before to treat the fish may have lost
their effect on the bacteria - and the run for an effective antibiotic may become a run for life.
But there are more problems. Handling in a tank with antibiotics (even if they are in the water in spurs)
will effect that very small portions of the antibiotics come into touch with the skin and on this way are
resorbed. This may make the antibiotic treatment useless if in other cases - with other illnesses where
antibiotics have to be used - it would be necessary. More and more bacteria become resistant against the
"normal" antibiotics which are normally used - and using them in aquarism supports this development.
Last but not least there is a direct risk. Allergic reaction as written before may be one - very quick and very
obvious - reaction, but there are many more chances for side-effects. Regular abuse of antibiotics may cause
severe damages. Just recently in Germany it was found that many cattle had been treated with
Chloramphenicol although this stuff is forbidden in the whole European community since at least two
years. Reason for the prohibition: It may cause severe damages of the spinal cord. When I was at HB's
wholesale maybe three years ago I saw that he used Chloramphenicol in kg cans and that a knife tip of
Chloramphenicol was added to every (!!!) bag of fish to be sent off.
Personally I strongly advice fish keepers (also in my books) not to use antibiotics except in very rare or very
expensive fishes and only exceptionally because of possible side-effects. That does not mean that I believe
that the use of antibiotics is useless - although it is as mostly done by unexperienced aquarists - none of
you of course ;-). However, most books recommend the use of antibiotics without telling about the riscs.
Hope I didn't bore you.
Harro
harro.hieronimus at t-online.de