Ich! in my 33 gallon

[naesco]

I would not risk putting any chemical in a reef tank. It will either not work or damage your coral.
If you have a QT you can remove the fish and try it there.
Otherwise I would suggest that you go to a health food store or a LFS and buy a bottle of garlic extreme or garlic extract.
Soak all the food you feed in garlic extract. Use dry food as it absorbs the garlic extract much better.
Feed only garlic soaked food and feed very often.
The idea is to get as much garlic into the fish as possible. The sooner you start the better.

BTW I happened to notice that you have a tang in your tank. It was likely one of the fish that show signs of ich. Tangs are ich magnets.

Tangs require large tanks because they are swimmers and need the swimming room large tanks provide and a 33 gallon is much much too small for any tang.
Please return the fish to the LFS or offer it to another reefer.
Good luck.