I realize this is an older thread, but for anyone else doing research: Def. try soaking in garlic. In my experience, it really helps to soak new food in garlic. After a few days of eating the new food with garlic, they seem to finally recognize the new source of food and then will readily eat.
Plus, any new fish will take some time to get used to the tank and may not eat during this time. Also, if all they got was, say, bloodworms before you got them, they won't recognize anything else as food at first.