Need help identifying disease!

[gats]

I have a reef tank with 1 Royal Gramma and 1 yellow Goby, a Sally crab, and a few blue-leg hermits and one snail. I am attaching pictures of my Royal Gramma that has some sort of disease. Started out with salt-like look on fins and body, only has a few now. Now it looks as if she has a film on her. She has one spot on top of her back that looks like it has eaten the first layer of skin and is getting larger. I hope you can tell something by the picture. She intermittently is staying by the return at the top of the tank, breathing somewhat laborered, and last night she started sticking her head out of the top of the water alot, and staying hidden more, but STILL HAS an appetite. The LFS made a house call and put two scoops of Metronidazole in the tank and told me to add to her food, too, and to continue this for a few feedings. I was already adding Kent's Garlic Extreme to her food. I'm not sure what he thinks the fish has, but said it didn't look like ich, but I see all signs of it. Any thoughts?? I don't have a hospital tank. Is the Metronidazole reef safe? Can you feed the garlic at the same time as Metronidazole? Please and thanks!

[harrison278]

Looks like marine velvet. if it is treat with copper

[gats]

Thanks for your input. I had a sneaky suspicion that could be it, but am still new at this. I don't have a hospital tank set up right now and can't put copper in since it is a reef tank, also. Would treating with Kent's Garlic Xtreme possibly cure this?? I've been giving it to her for the past 5 days. She has been swimming around alot today and is eating like a pig, but still has an UNEVEN look to her purple-ish body. I want to give her a freshwater dip tonight. Does anyone know if a freshwater dip would hurt if it is NOT ich? Please reply. Thanks.