I received a reply from Seachem, and was very impressed. Following is what they said regarding Kanaplex (hopefully it will help someone in the future!):
Seachem does not recommend use of medications for reef
aquaria, as various species in a reef tank may be more
sensitive than others in the system. It's unfortunate
that the local vendor gave you that advice. We never
advise anyone to use Kanaplex in a reef system. Typically,
used as directed, Kanaplex will not kill
beneficial bacteria within the live rock and water column
in addition to the nuisance/harmful bacteria and send your
tank into another ammonia/nitrite die-off cycle.
Any exposure to any medication creates additional stress
for any fish or coral as what occurred with your Xenia.
From what other customers have done relatively safely in
a
reef tank is dose Metroniadozle with Focus, soaked in
GarlicGuard. However, Seachem recommends that the safest
thing to dose in a reef system is to use GarlicGuard which
fish truly love (see
http://www.seachem.com/products/prod...licGuard.html).
If only one fish had a bacterial infection, then it is
best to set it apart in a quarantine tank as a marine tank
only and treat with Kanaplex or some other medications
such as Paraguard
(
http://www.seachem.com/products/prod...araGuard.html).
For scaleless fish, we don't advise using any medications
at all. The best thing for those fish is to simply soak
their food with GarlicGuard alone.
I apologize about your loss. If you have any questions
about treating your fish in the future, please contact us
first.
Thanks,
Seachem Tech Support