Weird plant growing on my drift wood

[seeto]

There's a weird black & white colour plant that's growing on my drift wood. I'm wondering if I should get rid of it or not. I've tried to remove it but it still comes back. Anyone knows what it is and if there's a need to remove it?

Here's a photo of it.

[boxedfish]

i got this from my bogwood. dont seems to be harmful and will disappear after weeks and then grow back on again. in fact i think they are pretty nice if they can grow more.