Friends fish, need help.

[MrLafogata]

Pearl gourami, I told her to quarantine but I don’t know anything else about this.

 

[MrLafogata]

No aggressive tank mates

 

[Jay Hemdal]

That looks like an aggressive bacterial disease. However, I’ve seen similar lesions that ended up being a cancer. Those take a long time to develop, so if this showed up in a week or so, it probably is bacterial. I guess I would opt for using maracyn 2 and Maracyn 1 at the same time. Best to do this in a treatment tank, but can be done in the main tank if need be.
Jay