Adding garlic is probably the best bet. The fish are attracted to really smelly food and usually the garlic does the trick.Jjust wondering though. Is the tank a planted tank? Often when you think a fish is not eating they are grazing on all of the live plants. They can do this even at night when you are not watching the tank.
My husband and I used to catch fish and eat them and I was the only one who knew how to clean the fish (husband grew up in el paso where there was no place to fish) and I finally said no more, only catch and release from now on. LOL.