Hey Velma,
We had a plague of these for a while in our small tank. They spread even faster than aptasia do. I think I found info for them under the term "orage ball corallimorph anenome" or something close to that, off the top of my head. If you search my posts with the right key words, you'll find I did a thread about them a few months ago.

The literature shows some conflicting reports, some even describe it as rare and unusual, but I can tell you that it spread like crazy and in my book that is not a good thing. We killed them with the same methods as we would aptasia, although they were slightly more difficult to get rid of than aptasia, in my opinion.

You're going to want to get rid of them eventually. I wished that I had not waited as long as I did to get aggressive about it, because they spread like wildfire overnight. Good luck. -Kristy