Anemone??

Question
I have a 90 gal that Im in the process of setting up. It is up and running and I am adding live rock as my wallet allows. My question is in regards to live rock. I have aprox. 30lbs in the tank so far and have noticed small what appear to be anemones on the rock. On one piece there are 3 small ones pink in color about the size of a dime(maybe a little smaller). At night when the lights are off there tentacles really come out. On some of the other pieces there are the same looking things but are clear or greyish in color. Any idea what these are and if I should rid my tank of them.

Answer
They are glass or rock anemones and can become quite a problem if they spread unchecked. These aiptasia are the food of several creatures, most notably berghia verrucicornis, a nudibranch which eats nothing but these anemones and will die without them so he must be passed on when his job is done. Also good at the task are red legged hermit crabs. If you want to try a beautiful fish, try the copperbanded butterfly. A great fish who loves aiptasia but must be in very good condition and eating when bought. Do not try to take them out while in the aquarium, they will break into pieces and multiply. You can also inject them with hot water through a syringe in the center of the mouth[top]. Let me know how you make out. Gerry.