I just buy a fresh garlic.
I take and cut a piece off then I remove the skin
I then take a morter/pestal and crush add in a little salt water from the tank and soak the frozen food in it for 5 minutes to 30 minutes but not more than 30 as the active ingreadient is allicin . The allicin is what is thought trigger the enhanced feeding response .
If you dont have a mortar/pestal you can use the back of a spoon on a plate/ dish ect . Then I take it to the tank turn off the filter and pour in most all of them will eat even the garlic bits as well ... HTH