Red Sore on Threadfin Cardinalfish

[Ross B Reef'n]

So after a a full QT schedule, I went to final inspect my school of threadfin cardinals before moving them to the DT. all looked good except this guy. Any ideas what this is?

 

[Jay Hemdal Verified Community Expert]

Tough to say - those guys are pretty sensitive to physical damage. I’d probably hold off a few days before releasing them for quarantine.
Jay