I am gonna guess some kind of goniopora. I'll try to find a picture to compare them to.
Here google this....
Notes from the trenches with Justin Credabel of fin and feather The Care and Propagation of Goniopora
Or maybe an encrusting Gorgonian
So are these things ok in my tank they are everywhere, i was going to zap them with joes juice but if they are ok and not harmless i'LL leave them alone