Your fish are smacking their lips! I usually flatten out that mixture, freeze slightly then slice into large squares for storage until ready to use, then when ready to feed, just slice off what is needed, defrost a bit in a water from your tank, then feed. Store in freezer. If you need to chop it up a bit more for smaller fish, I use one of those very small counter choppers, dump the food in with some tank water, chop it up.