Need ID: Is this white sponge a pest?

[nemokit]

Found this growing quite rapidly in my 4ft tank. Some growing on the rocks while a few big one (5mm long) are on my hammer coral.

Looks like a harmless, filter feeder but are these pests and should get rid of it?

[SubzeroLT]

These are pineapple sponge.

They are harmless filter feeders.

[patricklhc]

These are usually call pineapple sponge. Generally they are good filter feeders

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[nemokit]

Thanks "SubzeroLT" and "patricklhc". Didn't know they have a nice name too.