It is said that garlic helps the immune system. I am not sure if that is 100% true. IMO, it does help with finicky fish to take food. As far as defeating Ich, the answer is no. Also, UV will not kill Ich forever. If your display tank has a problem with Ich, you would need to leave it fallow (without fish) for a minimum of 8-10 weeks. If you have fish with Ich, I would recommend that you treat them, in a hospital tank, with either a copper treatment or hyposalinity.