GSP Hitchhiker

Hello all,

I bought a 4.5" piece of LR from the Diver's Den about a month ago. It has GSP encrusted on it.

I dipped it and it has been doing well. I notice some hitchhikers on it though. There are definitely a few tiny feather dusters. There also appear to be some kind of structure that sticks up taller than the polyps and waves in the current. It looks green and it looks like a piece of wheat. There are about 4 of them. They do not appear to bother the GSP. They do not look like pictures I have seen of hydroids (digitate or colonial). There are also a few tall, white/clear sponges on the rock. A picture will follow. Any ideas about those stalks that look like wheat?

Thanks