What are these?

[rags111875]

Folks,
My tank has been setup for ~5 months. Recently, these things are appearing on my sump glass (and skimmer and heater- not in my display tank, not in my refugium. Not sure what they are. Each is ~ the size of a fingernail. Started with one (as a hitchhiker, i must assume) and have expanded to ~50. Good/bad/indifferent?
They kinda look like some sort of filter feeder/feather duster.

 

[borg]

Looks like pineapple sponge harmless


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[rags111875]

Thanks Borg.
From your post, i looked up Pineapple Sponge online and that is definitely it.

Thanks!

 

[borg]

No worries I like em , easy to clean and remove if u don't like


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[SeaAgg09]

Yeah, these guys are totally harmless. The only thing I will say about any of these harmless hitchhikers, is they they can potentially start growing on equipment. Once a month or once a quarter, you should take out your equipment and soak it in hot water/vinegar and wipe off anything growing. While a pineapple sponge may not directly cause a pump to crash, long term neglect will cause a pump to fail long before it was meant to.