Unknown Growth on Tilefish

[Itchy Trigger]

I have a tilefish that has been in QT since arriving just over a month ago. He came down with what I initially believed to be Uronema marinum, and I began treatment with Metronidazole. His original symptoms disappeared and after 7 days of treatment I stopped dosing the metro. I then noticed a small oblong shape on his dorsal fin. His dorsal then proceeded to erode where that little spot was, and I became concerned again. He then began developing a weird growth at the base of where the eroded segment of dorsal fin was. This proceeded to erupt out of his back, looking like a rough, brownish grey mass, resembling a Grape Nut. I resumed treatment with metro (with daily water changes prior to each dose), but the growth has not gone away after over a week of additional treatment. Today the growth appears to be edged in red. I've attached a few pics (sorry for the quality - it's hard to get pics of him as he won't stay still).

He has continued to eat well throughout this entire ordeal, though today he ate with significantly less enthusiasm. Can anyone tell me what this is and how I should treat it?

 

[MrTuskfish]

I can't tell if this is a growth on the fish, or a parasite on the fish. If the latter, it looks like one of the many types of isopods and can easily be removed with a tweezers.

 

[Itchy Trigger]

I wish it were an isopod. It definitely appears to be some sort of growth. The fish is listing a bit and looking a little lethargic today and for the first time did not eat with vigor. I think whatever this is may be finally getting the best of him.