What is this?

[JSpilo]

Just noticed this on my guy today. It's possible it's been there for a minute and only just saw it. Only on one side.

I brought up the contrast levels in the photos so it could be seen easier.

It's almost like it's attached to its pectoral fin. Kind of hard to tell.

Any ideas would be appreciated!

 

[JSpilo]

Also, gills are not flared. Not gasping. Not skittish. It's swimming around happily and eating like there's no tomorrow. Flashing is rare.

 

[Man-made Monsters]

Could be a mark left from rubbing against something. I wouldn't be worried yet. But as always, keep the water clean and possibly add a small amount of aquarium salt.

 

[JSpilo]

Thanks for the reply. It's just worrisome. Looking at it more closely today it looks like it's attached to the inside on his pectoral fin.