Oodinium is another name for it. Looks like a fine sugar dusting on the fish's skin. You can really see it on their pec fins too. If you've got it, you gotta act fast. Hopefully there is a hospital tank big enuf for you inhabitants - considering there's coral and inverts in your tank. I've seen others mention Cupramine doses.
I lost 8 of 11 fish w/in two weeks time. Didn't know what velvet was and all were still eating. Thought I had fish playing in the sand - hence the coating. I treated with a product called Revive (coral and invert safe) twice within a week and maybe got lucky, but a yellow tang, watchman goby and a b/g chromis survived and are still doing great 5 months later. If you see it on the skin, it has already passed thru their gills. That's the SW
velvet. In FW
, it starts on the skin and then spreads to the gills, so there's more time to react, I believe.
Fluctuating water quality can be a huge culprit for an outbreak.
Anyway, good luck to you and keep us posted on your observations and success.