I woke up one morning turned on the tank light and shreeked... EEK.
Ever see an arrowcrab just sitting on the sand..without any legs? It's NOT pretty. I had no idea what happened. Asked my LFS what they thought and they said 'arrows will drop legs if water quality is bad.' um.. no. My water tested out fine.
Soooo... I bought another cute arrow crab, this time bigger. After 2 days what did I see? My female (she's BIG!) coral banded shrimp (CBS) had my arrow crab by the leg and was jerking him around. I immediately came to the rescue and seperated them. After loosing 2 legs, arrow crab got smart and started living in and near my anemone, which CBS feared. If CBS was 'stalking' arrow crab, arrow would run to the anemone.
The other day, I saw arrow crab sneak up on CBS, grab her antenna and run.. Arrow crab draged her around the tank like twice before letting go.
While I was laughing and cheering on my little arrow crab, CBS (who was QUITE miffed) chased arrow crab into the anemone then pinched at him at claw's length and got him out of the anemone. CBS chased arrow crab full tilt around the tank for like 2-3 minutes then went back to her house.
It's a never ending battle between these two. I asked some people I trust with regards to reef inhabitants and they all told me that this behavior was definitely normal, especially in smaller tanks where there isn't a lot of territory.