It generally is a result of growing the shrimp will molt and shed its exoskeleton. I leave the molt in the tank for my clean-up crew, but you can remove it if you want.
OK thank ... it really threw me off when I looked in my tank and had TWO cleaner shrimp. Had to take a second look. Right now it seems that the Bristleworms are dineing on it.
Mine molts about once every 3-4 weeks. The hermits and starfish race towards the leftover molt - whoever gets there first, wins. Usually it's the hermits.