black line on yellow tail damsel

[mrtian97]

I have a group of 5 yt damsels in my 120 gallon reef tank. I have them for 5 months, today I noticed that the smallest damsel has black line on one side of his body. he acts normal, eat, etc.
Any idea what caused this, it doesn't seems due to fighting. The group doesn't fight.

Thanks

 

[Humblefish]

Never seen that before, but I haven't kept damsels in many years. I'm thinking possibly he got cut up on your rock work.

 

[mrtian97]

thanks