[Jay]

I have dipped with Formalin dip. Bruce is right. Get the fish into quarantine. If you need to remove your live-rock then do so. How long has the fish been infected? Banish the finned friend to the hospital tank for 45 days to be safe. In the meantime I would get some vitamins and a good selection of grub for the rest of the fish in your tank. What I have noticed is that stress causes ICK. Working in the tank with your hands too much, like moving around your rocks too much or a power-head that fell into the sand causing a sand storm.Changing your water without matching the temp closely and matching the salinity of the water causes stress. You need to make your fish as healthy as you can. I use Boyd's Vita-chem on their food.
http://www.boydenterprisesonline.com...=1123599847805

You need to be feeding your fish a varied diet of seafood. Formula1 cubes and mysis. Soak the food in Boyd's for 15 minutes just before you feed them. The next day soak the food in Kents Garlic Extreme before feeding. I use Garlic once a week as a preventative thing and use Boyd's Vita-chem 2 or 3 times a week. This keeps my fish plump and healthy. They are too healthy and have a great immune system built up.

Look here for a great recipe for making your own fish-food from fresh seafood available at your safeway store. This recipe will provide a great variety in their diet.
http://www.melevsreef.com/food.html

Here is also a great page on how to feed your fish.
http://www.melevsreef.com/feedings.html

I know this may not help you with your 1 sick fish right now but keeping your fish as healthy as possible will keep them from getting sick.
Oh Yea!!! always keep your water quality high. Do the water changes religiously and use carbon to help keep the water clean.

Good luck and I hope your fish gets better.

Jay