Sponge with worm??

[TinnysReef]

Hi there,

These started as little nubs on my algae scrubber and now have grown little feathers like feather dusters. They look like sponges with tiny feather worms inside.

Are they pests?? They only seem to be on the algae scrubber so I can remove easily if they are.

 

[E.R.A.]

Its a pineapple sponge, a pest. I would get rid of them asap, but some people love them. My concern is them taking over.

 

[ISpeakForTheSeas]

Pineapple sponges (genus Sycon) - they are harmless (arguably even beneficial) filter feeders; they're common in newer tanks, and they tend to boom then bust in population before going away on their own.