Need help identifying odd invertebrate

[john007h]

I've attached a picture below of these odd round pink invertebrates that appeared on one of my live rocks. Not sure what they are, or if they are harmful/beneficial or what I should do with them.

Any help would be appreciated, thanks!

[sevenyearnight]

Whatever they are, they are a beautiful color!

[john007h]

Also my aquarium is riddled with feather duster worms all over the place (they are mating as we speak).
Should I start maintaining their levels, I'm worried they might cause the fish stress or deplete oxygen despite their filtering benefits.

[Pufferpunk]

Not sure but the pink looks like sponge. The feather dusters are excellent filter feeders, which will make your water cleaner. I've got them all over my fuge/sump.