Aiptasia
Hi Rich,I believe you have aiptasia in your tank,also called the glass anemone,Ive had a few myself,I brought in a couple of Peppermint Shrimps to get rid of them.Ive done a bit of research,and Ive read that injecting them with LEMON JUICE 3ml also gets rid of them.DONT break them off the rock because they will come back two fold.I dont know if anyone else has heard of this method with the lemon juice,but I prefer a natural remedy instead of chemicals.If you dont get rid they will eventually spread.