Looks to me possibly like a "tree" or arborescent foraminiferan, not uncommon in our reefs. Basically feeding on nutrients and microparticles. They can be exceedingly sharp however when you move rock around, but otherwise nothing to worry about.
thanks again Susan for your help. I researched a little about them but I couldnt find much info about them in aquariums or matching photos. I'll keep an eye on it and I'm glad to know its harmless besides it being sharp.
