Garlic- yes, no and how to use it?

Yes, it does help, you can just get a clove of garlic, and rub it on the food, or use other way to remove the juices. However, I would prefer to run a Quarintine, and treatfish in their with copper etc, to ensure such parasites as ich do not enter the main aquarium. Qt is also much safer to the fish, as you can treat with chemicals like copper, which could not be done in a reef tank.

some foods come with garlic in them as a special ingredient. It is usually advertised.

i use garlic guard by seachem.it is a liquid.it sells for about 9 dollars for 16 oz..i put a few drops on the food.

is there anyway to make liquified garlic at home ?

Proper quarantine procedures are worth more than all the garlic on the market. Although there is some evidence for garlic being a positive supplement for marine fish health and preventative for parasites, I am not aware of any serious scientific studies/results/data. Personally, I would never depend on garlic alone to resolve a cryptocaryon infestation. I have simply had too much success with copper and FW dips over the years. It is however, very good on crispy bread and I have tons of data to prove it.