Some sort of sponge? ID help needed please.

[dirtyreefer]

I would probably trust Bob's reply, it may look cool now because it's the only thing in your FOWLR, but once you get other corals in and stuff, it may become a pest that you may have a hard time to get rid of.

Even though I've never had that, it kinda reminds me of people that say that they have aiptaisia in their FO tank, and they think it's kinda cool and are wondering whether they should keep it