split peas. Buy some frozen peas...unflavored and boil some water in the microwave. Put a few peas in the water until they soften a bit. Then squeeze them to pop the shell off of each pea. This is a little bit tricky but once you figure it out it's easy. Now either put in both halves of your shelled pea or squish them up depending on the size of your fishes. lots of other veggies work too...