Sponge. Looks like Clathrina sp. I happen to like this variety. I usually leave a little bit and brush of the rest. If it's the species I think it is it will turn bright yellow with age. Those are young. Search Clathrina clathrus.Thanks! I will remove it . I did also noticed something like a white algae on my rocks…any ideeas what that might be ?
Larger spionids can definitely build tubes on the surface. There are also a number of vermatid species as well. Some of them can build tubes that are this size. They're just not seen very often. The small variety is far more common.Spionid dont build up tubes on the surface like what is seen in the pic. It's not a vermetid either. Those tubes are much smaller.