White "sponge" going to take over?

[canadian_eh]

Does anyone know what this is and if it will be taking over the tank? I can only guess that it is a sponge but I have no idea.

At first I thought it was dead but I noticed yesterday that it started growing over a small community of polyps.

Thanks for any help,
Ron.

 

[Bearfan]

I have an orange sponge that is growing like mad. I don't think I'll do anything about it as long as it keeps away from my corals.