About a week or 1.5 weeks, it got worse the first day or so but has not changed since but also not been getting better. Thought it might be a parasite or a tumor but that was just a guess.
Didnt want to stress the fish but i actually took it up to take a closer look, carefully poked with a pair of tweezers and this lump fell out. As of now, the fish seems fine. I hope it survives the night.
It is soft and squishy, i fear it might be an inner organ but the fish would have showed alot more stress by now right? Gall bladder and liver comes to mind, anatomically they are at the right place. Although the gills itself did not look damaged, but inflamed. Was hard to get a good look.
dropped the fish into the med-bay with furanol again. If it is fine by morning i might re-introduce it to the aquarium.
I still am unsure what it is, my guesses so far include inner organs, tumor, some sort of parasite, mucus or some sort of organic debris.