I have two starfish that came on an acan. I don't know if they are brittles or serpents and frankly the internet didn't define well the differences. They tend to hide with just a few tentacles out to grab food. I only saw them twice they are about the size of a fifty cent piece. I read some forum that serpents are not reef safe and brittles are with caution that they will eat fish and snails. Should I be concerned? The stars are red with strips and very thin arms.