Freshwater dips can get Ich off the fish, but it often gets in where a dip wont help. You might see the Ich on its body drop off, but it could still be untouched in gils, etc. That "treats", but does not alleviate, the problem. It also has to stress the fish, which is not good.
Garlic boosts immunity, but does not cure anything. Good idea to do, but does not touch the Ich. It will drop off, people think their fish was magically cured and what really happened was the Ich is still in the tank and can come back.
Copper treatment in a QT or hyposallinity are the ONLY two proven methods that work.