I can't see it well enough still. However, I can still make an educated guess.
If the "tree" is soft and quickly pulls into a tube or the rock, it's a harmless featherduster.
If it's hard, more than likely a foram. They are harmless protista. Sadly, this linked article doesn't contain a picture of a foram in the body style you are pointing out, but there is a foram that looks like that.
Foraminiferans by Ronald L. Shimek, Ph.D. - Reefkeeping.com