Help with Royal Gramma

[Kane32]

I recieved a Royal Gramma last Wednesday 2/13/2019 (ordered from LiveAquaria). I don't remember seeing this white line on the back end (see picture). Any idea what this could be? It's a straight vertical line. All other fish are fine. She is active and eating.
Tank is a RedSea Reefer XL 525 108 gallon with a 30 gallon sump.
Water parameters:
Ammonia 0 - Nirtites - 0 Nitrates 2ppm Red Sea Test kit

Tank mates are:
2 Ocellaris Clowns (small)
2 blue Green Chromis
4 firefish
1 lawnmower Blenny
1 brittle star
1 coral banded shrimp
13 nassarius snails
8 Trochus Snails
6 rred legger crabs
4 small blue hermit crabs

 

[ngoodermuth]

I can't make out much in the photo unfortunately, is it on both sides or only one? Any chasing or nipping from the other fish?

 

[Kane32]

I can't make out much in the photo unfortunately, is it on both sides or only one? Any chasing or nipping from the other fish?

Yeah sorry, that is the best photo I could get. It is only on the one side. I have not noticed any chasing or aggression.

 

[ngoodermuth]

If you can try to get a photo of the tail from the side that would be helpful.

I'm inclined to think it is just a scrape from a rock or aggression, but hard to tell. If its a scrape, clean water and vitamin-enriched foods should do the trick. If it looks like he is losing color, blotchy, or red I'd be concerned that it could be bacterial in nature.

 

[ngoodermuth]

This is an older thread, but a good example of what I mean by "blotchy/losing color" This royal gramma had a bacterial infection:
https://www.reef2reef.com/threads/royal-gramma-sick.286578/

 

[Kane32]

Here is a better pic

 

[ngoodermuth]

Ok, yes... I would definitely suggest pulling him to QT for antibiotics. It could possibly heal on it’s own, but it could also go south very quickly if left untreated.