White semi circle sponge like with tentacles on rock.

[GTAReefTank]

It’s fixed on the rock. I think I see another smaller one on another rock.

 

[Ron Reefman]

Are you just looking to get an ID?

I think you may need to get a better photo. Shine a light (flashlight, cell phone, whatever) on it and try another pic. That may help a lot.

 

[samnaz]

I agree, another photo with more light would be helpful.

A couple questions/details to help to narrow it down... are the tentacle-like structures always extended and do they retract if disturbed? Also how large is it?

Best guess based on the photo, almost looks like palythoa...

 

[GTAReefTank]

Thanks guys! It’s base is just a little bigger than a quarter and forms a dome shape. It’s white. The tentacles are always extended. I haven’t tried to disturb it yet - it seems to stay in one place (same place in the last 2 days).
Unfortunately it’s in a dark area of the tank.
Here are more pictures.

 

[GTAReefTank]

Yes, looking for ID

Are you just looking to get an ID?

I think you may need to get a better photo. Shine a light (flashlight, cell phone, whatever) on it and try another pic. That may help a lot.

 

[DanConnor]

Pineapple (sycon) sponge at an odd angle?

 

[samnaz]

Looks like a Pineapple sponge.

 

[GTAReefTank]

Thank you @DanConnor and @samnaz !
Did a quick google image search and found a few that looked exactly like mine.

Harmless filter feeders and possibly an indication of high nutrient load from what I read online.

Looks very much like this one in this link.
https://www.reef2reef.com/threads/pineapple-sponge-explosion-good-or-bad.538748/
Thanks again!

 

[samnaz]

Thank you @DanConnor and @samnaz !
Did a quick google image search and found a few that looked exactly like mine.

Harmless filter feeders and possibly an indication of high nutrient load from what I read online.

Looks very much like this one in this link.
https://www.reef2reef.com/threads/pineapple-sponge-explosion-good-or-bad.538748/
Thanks again!

you're welcome, happy to help