Help me save my damsel!

[thormx]

My damsel has not been himself lately. I noticed it about a week ago. The first thing I noticed was that he was having trouble swimming normally. He's usually very active doing laps around the tank all day long. Now he just kinda hangs around in one area or sometimes in the corner. He had also been very jumpy when I walk by or when I try to get close for inspection. He also now has a spot on either side of his dorsal fin that looks like it is rotting away. This is new I have just noticed it today. I was thinking a swim bladder infection possibly due to his trouble swimming normally. I plan on putting him in a hospital tank and medicating, but I don't know what medication I should use or if that's really what I should do. I've had him for a couple years now and don't want to lose him! Thanks for any help!
Ps I'll try to get a pic up of the fin erosion.

 

[TurboReef]

Definitely needs to go in a hospital tank. You could try a short FW dip followed by treating the hospital tank with cupramine.

 

[Humblefish]

You saying the fin looks like it's "rotting away" and "fin erosion" suggests this fish has a bacterial infection. Once you get him into QT, you can treat with a broad spectrum antibiotic such as Furan-2 or Kanaplex for that. However, bacterial infections are often secondary in nature to a preexisting parasitic infestation such as ich, marine velvet, brooklynella or uronema. If present, those need to be addressed with something other than antibiotics. Have you added any new fish lately? Have you ever seen ich (i.e. white spots) on any of your fish?

 

[thormx]

Thanks I'll look into that. Here are some pics.

 

[Humblefish]

Is that "rot" on the skin itself? On the dorsal fin, near the back?

 

[thormx]

I have never seen ich in my tank. The last fish I added was a puffer a few months ago. Every other fish seems happy and healthy.
The rot looks to be on the the scales rather than the fin

 

[Humblefish]

I would treat with antibiotics in QT to get the infection under control first, and then go from there. If you feel confident there are no parasites in your DT, he can go back in once he's looking better.