There are several garlic preparations available. I use GarlicXtreme which is an extract. You put two drop onto food and place it in the tank.
The problem you have now is that you have Ich in your tank. It can now infect all other fish in the tank. You really need to get all fish into a QT tank and treat there (hyposalinity IMO) while the main tank remains fallow of fish for 6-8 weeks.
The tang was never in the display, only in the quarantine, and that tank will follow through with hypo treatment. Thanks for the links, I will take a look at them when I get home.