It does sound bacterial as they stated but does not sound serious enough to put the fish through QT
and medication. See your water test kits can't help with DOC
in the water which causes this. What can help is a bunch of water changes and cleaning. Perform 3-4 large water changes with mixed (24hrs) and aerated sw
, temp, sg
) - do one every few days for the next few weeks, then once a week after. Clean any filters or areas that may collect waste. Run activated carbon or a polyfilter to help clean the water further. Just keep up on these water changes and he will heal on his own. It will take a few weeks, but the fins will come back like new. This is easier and safer than going the QT
route. This also addresses the root cause - high DOC
in the water which the bacteria thrives on. Meds would only be a bandaid anyway.
Do you run a skimmer? A skimmer removes DOC
from the water which causes this kind of bacteria build-up. A good thing to have. Frequent water changes will do the same thing.
NEVER use meds in the main tank (reef tank or not), especially an antibiotic, it can zap your biofilter throwing your entire tank out of balance which could kill everything.