Need help with ID

[Rython]

Bought a purple firefish yesterday. Last night I dosed the QT with Paraguard. This morning he has what appears to be grey lint hanging from a pinprick sized hole behind his pectoral fin on one side. It's also very close to his gills, so it could be hanging from there and the hole is unrelated, but his breathing is normal. Any help with ID and treatment options would be appreciated. Should I attempt to manually remove?

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[Rython]

More photos

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[Rython]

I'm leaning toward fungus based on internet descriptions, and either continue with Paraguard or try Sulfaplex. I'm a total novice though, so if anyone has an experience and would like to help guide me, it would be appreciated.

 

[Rython]

Serpentisaccus Magnificae maybe?

 

[Rython]

Well, I decided it was probably Serpentisaccus Magnificae. Since I couldn't find any information on successful interventions, I contacted the LFS and they reluctantly allowed me to return it for store credit.

However, when I brought it back they put it right back into the "for sale" system, which seems pretty likely to infect every other firefish they have with the parasite, since what I was seeing was the egg sac hanging out of the fish's body. I also identified (again as a novice) a couple of fishes with fin rot, one in internal bruising (bacterial infection?) and a maroon clown that appeared to have Brook. Needless to day, that store credit will be used for fish food or something, and i'll be looking for a new LFS.