Not sure what this is....

[BryanDuggan]

This is semi hard, has no polyps or tentacles, grows back when I break it off, and a bit of a mystery to me? Any idea??

 

[Zippy69]

Are you talking about the tube worms, coraline algae, sponge...or the anemone?

 

[BryanDuggan]

Good point. The beige thing.

 

[saltkreep88]

Sponge, they are beneficial and harmless.

 

[redfishbluefish]

Are we talking about this guy circled in red?

My guess is that it's a sponge.

 

[BryanDuggan]

Yes. It was the size of a ping pong ball. I broke it off a few months ago (had a consistency like hard cheese) and it has grown back.

 

[Chex_Mix]

Yup, looks like a sponge to me. I use to try to remove them from my sump because they got pretty big, but then I just gave up because I would take one out and then I would get two more. They just seem to reproduce very fast in my tank

 

[BryanDuggan]

Thanks everyone. I think I'm going to leave it alone.