Help identify this stuff?

[kyleshaw81503]

What is this white ashy looking stuff at the base of my Duncan and how do I get rid of it?

 

[Crabs McJones]

Look like hydroids

 

[vetteguy53081]

Im seeing clatarina sponge and colonial hydroids
Both can be scraped off in a container of tank water

 

[Double monti 61]

If it does not bother the Duncan maybe it is not harmful to your system one thing I believe to many people worry about all the small life that shows up in their systems and in the real world they exist in their natural habitat and if their numbers stay in check then I think they are more beneficial than detrimental.