colonial hydroids

These things have been here for over 2years now when i first bought the tank. Havent seen them anywhere else in the tank.The green circle gets much brighter when lights are on.

Hi everyone, I am a new reefer and new to reef2reef. After cycling my tank and adding my first fish, I thought it was finally time to take the plunge into corals. I bought a beautiful green ricordea covered rock from LFS, unfortunately though it has also come with bristle worms, and whatever...