Identifying Mystery Thing

[NoMu Fish]

I am not sure what this is. Someone please help. This has appeared in my tank with just corals.

 

[jeffchapok]

Harmless sponge

 

[pseudorand]

Looks just like what I think is a pineapple sponge in my tank. Your picture is better than mine.

Thread 'What's this white cone thingy?' https://www.reef2reef.com/threads/whats-this-white-cone-thingy.763870/

 

[elysics]

Some kind of Tethya sp. most likely. Look at pictures of Tethya gracilis

 

[jeffchapok]

I don't think it's a pineapple. I've had pineapples and I've had one like this as well. They are different. But they all went away in time in my tank. I had hoped to keep this one - I thought it was interesting.

 

[jeffchapok]

Some kind of Tethya sp. most likely. Look at pictures of Tethya gracilis

I'd say you nailed it.