I had a similar problem with my Gouramis....
Unfortunately fungus is usually a result of a bacterial/parasitic infection or the fish has damaged itself on a tank object.
Here is how i successfully treated my 3 opaline gouramis (the first time anyhow).
I added the gouramis to my Quarantine tank and let them settle for a day.
I then added some Methylene Blue which i think is a 7 day course.
To increase its effect i added 1/2 dose of Melafix on the 3rd day, so it would overlap by 3 days. This will help heal the wound after the fungus is gone too.
On the 3rd day i also started to add aquarium salt to increase the effect of the meds. I added gradually up to 0.9%. The levels stated to aid disease treatment.
I left the meds in the tank for rerquired time.... which in total was 10 days.... i then added carbon to the filter and did water changes to get rid of meds. Then a few days later i added them back to the tank........ (in total QT 14 days)
This worked a treat and the fish are now healthy and living, looking great again. 1 of my Gouramis died a few weeks after due to the phanton ulcer gourami disease which i still have not gotten to the bottom of.
Methylene Blue is an old treatment, and unless used with salt is pretty useless for treating fish. However i found it effective using the above methods.....
Good luck and I hope this helps...
Remember softly softly catchy monkey
