Anthias with something on fin

[Dorado]

A couple of days ago, one of my lyretail anthias developed a spot of some sort on its tail maybe an 1/8" long. Today the the area of the fin where the spot was is completely gone. The fish is eating and acting fine I just wanted a proper diagnosis and treatment plan. I've tried to search and the best I can tell is that it is bacterial? I've been checking water parameters like crazy every day since, but everything has been good. None of the other fish are exhibiting any symptoms yet.

 

[fishguy242]

@Jay Hemdal @vetteguy53081

 

[vetteguy53081]

How do the other anthias look? Appears to be both lympho on the fin and brook or similar on body which questions water quality and diet
What is she of tank, current parameters and food being fed?

 

[Dorado]

Like I said, the one anthias is the only fish showing symptoms. The tank is a 150g, 6 anthias, yellow tang and a clown. There isn't anything on the body, maybe a bad picture, just the dorsal fin. Being fed a blend of mysis and rod's food soaked in selcon.
0-ammonia
.5-nitrate
8.1-ph

 

[Jay Hemdal]

A couple of days ago, one of my lyretail anthias developed a spot of some sort on its tail maybe an 1/8" long. Today the the area of the fin where the spot was is completely gone. The fish is eating and acting fine I just wanted a proper diagnosis and treatment plan. I've tried to search and the best I can tell is that it is bacterial? I've been checking water parameters like crazy every day since, but everything has been good. None of the other fish are exhibiting any symptoms yet.

Do you mean the notch in the soft part of the dorsal fin? That is likely a bite from another anthias that has gotten a secondary bacterial infection. It may heal itself, but the fighting can continue, or even get worse. Sometimes, groups of anthias just don't work out. I presume the fish picture was taken earlier than the second one, that shows me the advancing infection.
The treatment would be to move the fish to a treatment tank and dose with a broad spectrum, gram negative antibiotic such as Furan-2 or Neoplex.

Jay