David: I hate to be the barer of bad news, but if you are seeing ich on one fish, you have it in your system and you are going to have to take action, or always have it. The garlic most certainly helps, but if you really want to do things right, you're looking at trapping some fish and a six week minimum hypo/fallow session.
Don't tear up your reef. It's not as hard to trap fish as you think, but you have to do it while they are still eating. If you wait till the ich gets bad enough that the infected fish lose their appetite (and they will) you'll never be able to trap them.
The club has a few nice traps for members to borrow, that make the circuit continuously, or you can make one very easy from one of those plastic jars that Activated Carbon comes in. If you only have six fish in that tank, I'd definitely get busy trapping them.
Right now you should be soaking a sponge in your sump and cycling your QT tank. Don't fall into the trap of complacency. The spots may disappear for a while, (They WILL disappear) but they will be back, probably at the addition of any new fish or any stressor presented to the tank. PM me if you have any questions about Hypo/Fallow after reading the sticky threads, or if you need help making the DIY trap. Better yet, I have several, you can have one. I also have a 20 gallon QT cycled and ready if you need help.
Here's the container you need:
DIY Trap