Another ID question

[Will C]

These have shown up in my sump. My tank was set up in October, I've added some caluerpa from my lfs and a macro algae from a rc seller. Nothing is showing in the display tank. Any idea on what it is?

 

[Dkuhlmann]

Pineapple sponges, a harmless filter feeder. It's also a testament that you have good stable water conditions.

 

[Will C]

That was fast - thanks